One day after beheading an abducted South Korean, underground Islamic extremists vowed Wednesday to assassinate Iraq's interim prime minister, Ayad Allawi, and pursue their campaign of bombings and kidnappings until they drive U.S. occupation forces from the country.

The threat, made in an audio recording posted on a Web site often used to convey such messages, was attributed to Abu Musab Zarqawi, a Jordanian linked by U.S. officials to the al Qaeda network of Osama bin Laden. Occupation officials have accused Zarqawi and his followers of being behind many of the car bombings that have plagued Iraq in the lead-up to the transfer of limited authority to Iraq's interim government on June 30.

"As for you, Allawi -- pardon, the democratically elected prime minister -- we have prepared for you a potent poison and a sharp sword and have filled for you an intoxicating cup, full of the smell of death and the odor of mortality," the man identified as Zarqawi said, mocking the appointment of Allawi to his post three weeks ago by U.N. and U.S. officials.

"Without knowing it, you have survived well-placed traps we set for you, but we promise that we shall follow our cause to the end. Unless we die first, we shall neither tire nor despair until we make you drink from the same cup as we made Izzedin Salim drink from."

Salim, who was taking his turn as president of the now disbanded Governing Council appointed by U.S. occupation authorities, was killed by a car bomb as he approached the heavily guarded government and occupation headquarters on May 17.

Allawi, as interim prime minister and close collaborator with the U.S. occupation, has long been a likely target for assassination. The opposition group he founded in exile before the fall of President Saddam Hussein was funded by the CIA. He was a member of the Governing Council and now has the top office in the interim government. Deputy Defense Secretary Paul D. Wolfowitz on Tuesday called him "number one on the enemy target list."

Allawi only occasionally ventures outside the government headquarters area called the Green Zone in central Baghdad. When he does, rifle-toting security agents surround him. But he said Wednesday that Zarqawi's threat would not deter him from carrying out his duties.

"The prime minister does not care about such statements from Zarqawi," said a statement from his office. "He will continue with his work, to bring democracy to the people of Iraq."

Zarqawi's organization, which calls itself the Monotheism and Jihad Group, asserted responsibility for the beheading on Tuesday of Kim Sun Il, 33, a South Korean contractor who worked for a firm supplying the U.S. military in Iraq. The group also announced that it carried out last month's beheading of an American businessman, Nicholas Berg, who was abducted in northern Iraq.

Several hours after American soldiers found Kim's body and severed head on the road between Baghdad and the rebellious city of Fallujah, the U.S. military launched an airstrike against a house in Fallujah that it said was being used by Zarqawi's fighters. A senior U.S. military official estimated 20 foreign insurgents were killed in the attack. A similar strike Saturday also killed about 20 people, including women and children.

Early Thursday morning, insurgent forces staged major attacks on Iraqi police stations on the outskirts of Baqubah, 40 miles northeast of Baghdad, and in Ramadi, 60 miles west of the capital. Initial reports from the area said about 20 policemen were killed in the clashes. At the same time, local journalists told Arabic-language television stations that U.S. helicopter gunships fired on targets in Fallujah, the rebellious city about halfway between Baghdad and Ramadi, and a number of U.S. armored vehicles were seen headed in that direction from nearby Marine encampments.

A streetside bomb in downtown Baghdad on Wednesday killed two people and wounded several others. An Iraqi policeman, 1st Lt. Basim Ibrahim, said the bomb was inside a cardboard box that sat in front of a watermelon stand and exploded when a boy alighted from a donkey cart and picked it up. The blast killed the boy and a woman who was passing in a taxi that was set on fire by the blast, Ibrahim said.

"They might be saboteurs who came from abroad because they don't want stability and security for this country," Salih Joda Hemoud, 30, a truck driver, said near the bombing scene.

His speculation coincided with the impression U.S. and Iraqi officials have been trying to create about the campaign of violence in recent weeks: that outsiders have been the decisive factor, seeking to frustrate the desire of most Iraqis to set up a new, democratic government as urged by the United States.

"If half of what is attributed to him is true, then he is the most significant terrorist in Iraq at this time," the senior U.S. military official said of Zarqawi.

The statement attributed to Zarqawi, widely reported here on Arabic-language television networks, appears likely to encourage that view among Iraqis, many of whom have expressed reluctance to believe that their countrymen could be behind the suicide car bombings.

Weheb Hassan, 32, a crane operator, said he believed that the Bush administration was not unhappy with bombings such as Wednesday's because it does not really want to leave Iraq, with its oil reserves and strategic location for future military bases.

"As long as the Americans stay, the explosions will continue, whether they transfer sovereignty or not," he said. "They don't want the situation to stabilize."

An Iraqi soldier was killed by another roadside bomb in Mosul, about 215 miles north of Baghdad, a day after the killings of the dean of the college of law at Mosul University and her husband. Two policemen were shot to death in a drive-by shooting near Ramadi, 60 miles west of Baghdad, authorities reported, and in the far south of the country, two women who worked for the British military in Basra were shot as they drove home Tuesday evening.

Also, efforts by Shiite Muslim religious and political leaders to draw defiant cleric Moqtada Sadr and his followers into the political process suffered a setback. A spokesman for Sadr said the cleric would not participate in a national conference scheduled for next month unless its formula for representing Iraq's diverse political and ethnic currents was changed.

"After many discussions among ourselves, Moqtada Sadr's office announced it will not be able to attend the national conference session, for many concerns," said Ahmed Shaibani, a Sadr spokesman in Najaf, a Shiite holy city about 90 miles south of Baghdad. "One of the most important is the procedure adopted for representing different people."

Fuad Masoum, a Kurd who is organizing the conference, said he had not yet sent out formal invitations. The national conference has set as its goal choosing a body similar to a legislature that would monitor the interim government and help organize elections planned for next January.

Special correspondent Huda Ahmed Lazim contributed to this report.

An Iraqi walks through debris in a parking lot after an overnight U.S. airstrike in Fallujah, west of Baghdad, that a U.S. official said had targeted a house used by foreign insurgents.