Six rockets, launched by remote control from empty vehicles, were fired almost simultaneously today at the U.S. Embassy and other American and international buildings in the Pakistani capital of Islamabad. Several people were injured, including a Pakistani guard at the American Cultural Center.

The rockets fell short of their targets and caused little damage. No one claimed responsibility for the attacks, and Pakistani authorities said they had no suspects.

Pakistani officials and observers speculated that the assaults might be linked to supporters of the radical Islamic Taliban regime in neighboring Afghanistan or extremist Saudi financier Osama bin Laden, who is being sheltered there by the Taliban and is suspected of masterminding the bombings of two U.S. embassies in East Africa in August 1998.

U.N. sanctions are scheduled to be imposed Sunday against the Taliban for harboring bin Laden and refusing to turn him over to U.S. authorities. The Taliban are supported by a number of Islamic extremist groups in Pakistan.

The rockets apparently were launched from parked vehicles, which were found ablaze, and appeared to be aimed at the World Bank building and the Saudi-Pak tower, which houses U.N. offices as well as at two U.S. facilities.

Witnesses described seeing a car burning about 75 feet from the cultural center, a busy facility that houses the U.S. government's cultural and public information activities. A second car with a U.N. license plate also was on fire near the U.S. Embassy; it wasn't clear how that fire began.

The explosions injected new tension into the month-old rule of Gen. Pervez Musharraf, who overthrew civilian prime minister Nawaz Sharif in a bloodless coup Oct. 12. Sharif was charged with treason this week and might be tried in military courts and sentenced to death.

Musharraf was quoted today as calling the attacks "quite serious."

In Washington, State Department spokesman James P. Rubin said the incident will be thoroughly investigated and refused to rule out involvement by the Taliban.

Rubin also vowed that the economic and travel sanctions against the Afghan government would go into effect "if the Taliban does not assist in bringing Osama bin Laden to justice." The U.S. Embassy and related facilities will remain open in Islamabad but will operate under "a heightened state of alert," he said. A U.S. Embassy spokesman said all Americans in the U.S. facilities were safe.

Taliban leader Mohammad Omar criticized the bombings, saying his regime "has always condemned terrorism and continues to condemn it."

Noting that the blasts came shortly before the U.N. sanctions are due to take effect, Omar said he believed they were intended to undermine relations between Afghanistan and Pakistan, the United States and the United Nations. He urged authorities to "pinpoint the enemy" behind the attack and expose its motive.

Pakistani Interior Minister Lt. Gen. Moinuddin Hyder said "there should be no doubt that we will never allow the Taliban or any other group to settle their score with the U.S. or the U.N. on our soil." He said that while this was the first time terrorists had used remote-control rocket launchers inside Pakistan, there are "numerous groups in the country who have the ability to launch such an attack."

This week thousands of angry Afghanis protested plans by the U.N. Security Council, strongly backed by the Clinton administration, to impose the sanctions on the Taliban regime if it fails to hand over bin Laden, the fugitive Saudi financier who has sworn to wage a holy war against the United States.

American authorities believe bin Laden masterminded and financed the bombings of the U.S. embassies in Kenya and Tanzania, which killed 224 people.

Taliban leaders, whose war-ravaged country desperately needs foreign aid and investment, have hinted that they might be willing to expel bin Laden. But in recent days their stance has hardened and they have adamantly refused, saying Islam forbids them to mistreat a guest.

Taliban leaders warned this week that if the U.N. sanctions are imposed, the United States and other Western powers could face divine retribution, such as storms and earthquakes. The Islamic group is ardently opposed to Western influence in the Middle East.

According to senior security officials in Islamabad, intelligence reports over the past two months have suggested that a group of pro-Taliban militia members might launch a terrorist strike against Western targets in Pakistan. After the October coup, one official said, such security concerns "got swept away."

On Wednesday, about 50,000 Afghans demonstrated in Kandahar, the city that serves as Taliban headquarters, burning American flags and throwing stones at the U.N. building.

The U.N. sanctions would effectively cut off all flights to and from Afghanistan, except for humanitarian or religious reasons. They also would freeze the Taliban's overseas assets.

Pakistani officials speculated that the attacks could be linked to Lashkar, a Pakistan-based Islamic guerrilla group that held a three-day annual meeting near Lahore last week. Speakers excoriated the West and vowed to intensify their "holy war" against Western interests. The group is waging a clandestine war against security forces in Kashmir, a territory claimed by India and Pakistan.

Constable reported from New Delhi, Khan from Karachi. Staff writer John Lancaster in Washington contributed to this report.