Declaring their readiness to die for their cause, Chechen rebels holding a theater audience of up to 700 people captive in the heart of Moscow threatened Thursday to begin killing them if Russia did not withdraw troops from the breakaway southern republic of Chechnya within a week.

The militants promised this morning to release the foreigners inside, believed to number about 75, including three Americans, according to Russian officials. The rebels had made similar promises previously but not followed through.

Russian officials said this morning, however, that they had reached a final agreement. A Moscow city official, Mikhail Antontsev, said the foreigners were expected to be released about 9 a.m. (1 a.m. EST).

Representatives of foreign embassies had been asked to arrive near the theater. The U.S. ambassador to Russia, Alexander Vershbow, expressed optimism after arriving about the chances for the Americans' release.

One person was killed Wednesday night in the initial assault by as many as 50 masked guerrillas armed with assault rifles and explosives strapped to their bodies.

One of the hostage-takers was seen in a video shown on the Arabic-language satellite television network al-Jazeera declaring readiness to die.

"I swear by God we are more keen on dying than you are keen on living," the hostage-taker said. "Each one of us is willing to sacrifice himself for the sake of God and the independence of Chechnya."

"Even if we are killed, thousands of brothers and sisters will come after us, ready to sacrifice themselves," a female militant, her face covered except for her eyes, said on the same broadcast.

On Thursday afternoon, on-again, off-again negotiations brought the release of five hostages, and the rebels later released the body of a woman in her twenties who authorities said was shot to death in the early hours of the crisis when she defied her captors.

Early this morning, seven more hostages were released, said Sergei Ignatchenko, a spokesman for the Federal Security Service. He refused to release any details.

Sporadic gunfire and explosions were heard from the scene at various times Thursday, but reports were sketchy about what was happening. At one point, Russian media reported that militants fired rocket-propelled grenades out the window of the theater as two young women were making their escape, injuring a Russian soldier.

The rebels have fastened explosives to chairs, columns and other parts of the theater, according to some reports from inside.

Hundreds of heavily armed Russian troops, police officers and special forces surrounded the theater but held back from storming the building, which is located in southeast Moscow, three miles from the Kremlin. Reports indicated that about 45 children remained inside the theater.

The hostage crisis gripped Russia, which has not seen such a dangerous confrontation in the middle of its capital since the tumultuous early 1990s.

More than 24 hours into the ordeal, a few hostages managed to call out on cell phones to report the atmosphere inside was deteriorating. "The tension is escalating," said one of them, Maria Shkolnikova. "The demands of the terrorists are turning into an ultimatum."

She told Echo Moskvy radio that the situation could soon turn bloody. "They say, 'You have been sitting here for more than 10 hours and your government has done nothing to release you,' " she recounted. "The main thing they need is a troop pullout from Chechnya. If there is no pullout, they will start shooting people."

Soon, one of the hostage-takers took her phone. Calling himself Hasmamat, the Chechen rebel said to Echo Moskvy: "Our demands are of the very simplest: Stop the war and withdraw the troops." The live interview brought the radio station a reprimand from Putin's government, which has prohibited broadcast media from giving airtime to the hostage-takers.

Later this morning, the militants issued a new demand, calling on relatives of the hostages to organize an anti-war protest in Red Square. A woman who identified herself only as Nadejda said her 23-year-old sister called her from inside the theater to relay the demand.

Within two hours, relatives were waiting for a bus organized by Moscow city officials to transfer them to the square. They were carrying pieces of rolled-up wallpaper, on which they had written anti-war slogans.

In his first public remarks on the standoff, Putin said that "the criminals, of course, are provoking us to introduce the same order in the country as they once imposed in the Chechen republic. We will not give in to this provocation." He added that "the safety of people is the most important thing at the moment."

Putin, who spoke with Bush by telephone, said the seizure of the theater was planned by foreign forces and connected it to the recent bombing in Bali and attacks in the Philippines. "The same people planned the terrorist act in Moscow," he said without offering evidence. The Interfax news agency quoted an unnamed law enforcement source as saying the hostage-takers had been contacting accomplices in Turkey and the United Arab Emirates.

For Putin, the impasse brought home the trauma of the brutal battle in Chechnya, where Russian troops have waged two wars over the last decade in an unsuccessful campaign to smother separatist ambitions. No longer just a conflict nearly 1,000 miles away, the war has now confronted Putin with a dilemma at his own back door: If he seeks to negotiate with suicidal militants, he would face demands he presumably would never meet. If he seeks a military option, there could be a bloodbath.

Previous hostage-takings by Chechen militants have not ended well. In 1996, rebels took more than 2,000 civilians hostage at a hospital in Dagestan; most were released, but in a week of fighting that followed, dozens of combatants were killed. In 1995, more than 120 people were killed in a similar raid in the town of Budennovsk near Chechnya.

Second-guessing and political backbiting began even as the crisis continued. "We find ourselves to be hostages of a weak government," the leader of the Communist Party, Gennady Zyuganov, complained Thursday. Other opposition politicians repeated earlier demands, long ignored by Putin, for peace talks with the Chechens.

The only known fatality came at the outset of the crisis when a woman in the audience either refused an order or tried to escape, according to authorities. A female militant shot the hostage, whose body was recovered from the building Thursday afternoon with a bullet in the chest and broken fingers.

Later on Thursday, two female teenagers made a break from the theater, prompting gunmen to fire grenades at them. The pair escaped, but the explosions injured a Russian soldier, authorities said.

The prospects for negotiations remained uncertain. A prominent Russian legislator was allowed into the theater twice Thursday to talk with the militants and reported seeing a masked woman with a remote-control device in her hands who threatened to blow up the building.

Accompanied by Red Cross representatives, Yosif Kobzon, a member of the State Duma as well as one of Russia's most famous singers, secured the release of five hostages just after 1:30 p.m. They were an ailing British man in his fifties or sixties, a woman and three children. The second time he went inside, however, the militants refused to release anyone else.

"When I asked them to release somebody else, they told me that they had released the three youngest ones and would release no one else," Kobzon said. After the talks, Kobzon told a colleague, "It's very hard to talk to them; they're fanatics."

A lawmaker who accompanied Kobzon during the second visit, Irina Khakamada, left immediately afterward for the Kremlin to brief officials on the discussions. An aide said by telephone that the guerrillas told Khakamada that they did not want to deal with intermediaries and wanted to talk only with people who hold real power. Late Thursday, one liberal lawmaker, Grigory Yavlinsky, went into the theater for negotiations and stayed about an hour. Another group of negotiators went in with their hands raised just before 10 p.m.

In addition to the three Americans and a Russian with a U.S. green card, other foreign hostages included citizens of Britain, Germany, Austria, Switzerland, Australia and the Netherlands.

U.S. Ambassador Alexander Vershbow said one of the American hostages called the embassy from inside the theater before dawn Thursday and talked with a Marine guard, while another reached relatives in the United States who then passed along the information to Moscow. The embassy would not identify them beyond saying one was a man and three were women.

The drama began shortly after 9 p.m. Wednesday when dozens of Chechen rebels wearing camouflage uniforms and masks stormed the theater on Melnikova Street, still known by its full Soviet-era name, the House of Culture for the State Ball-Bearing Factory. Taking control of the building at the start of the second act of a popular musical, "Nord-Ost" ("North-East"), they fired guns into the air and began planting explosives, according to witnesses.

Federal authorities said 46 hostages have been released since the beginning of the crisis, while about 100 others evidently escaped through windows or back doors during the early confusion, leaving the Chechens with about 700 captives. Several of the militants are women, according to authorities and witnesses.

The hostage-takers were led by Movsar Barayev, a largely obscure figure on the radical fringe of the Chechen separatist movement and the nephew of a Chechen warlord, Arbi Barayev, who was killed last year. A government official told Russian television that a man presenting himself as the spokesman for the gunmen gave the name of Abu Said and said he was with 50 militants, half of them men and half women, all of whom considered themselves shahids, the Arabic word for martyrs.

A foreign journalist who managed to get into the theater lobby on Thursday for 20 minutes with Kobzon, and later returned to interview Barayev, said the militants appeared unwavering in their main demand. "We've come to die," Barayev told the reporter, Mark Franchetti, of the Sunday Times of London. Franchetti said he saw three female guerrillas with explosives strapped to their stomachs. Later, NTV television broadcast footage of those guerrillas carrying pistols and dressed in black. "They say they're shahids, martyrs. It's difficult to know, but they're pretty determined," Franchetti added.

Correspondent Sharon LaFraniere contributed to this report.

Russian troops stand guard outside the Moscow theater seized Wednesday night by Chechen separatists with explosives. At least three Americans are among the 700 or so hostages.