A powerful car bomb rocked a busy market area in the center of Kabul on Thursday, killing and wounding scores of people in the bloodiest attack in the Afghan capital since the fall of the Taliban.

The attack came just a few hours before President Hamid Karzai and a powerful regional governor survived an assassination attempt by an Afghan security guard who fired on their convoy in Kandahar.

Police said at least 10 people were killed in the Kabul bombing. A U.N. security official said 22 were dead.

About 65 people were rushed to one hospital, with an unknown number taken elsewhere. The death toll was uncertain because Afghans often pick up the bodies of their relatives and bury them immediately without reporting the death.

Emergency vehicles and armored personnel carriers from the international peacekeeping force rushed to the scene in a crowded market area near the Ministry of Information.

Witnesses said a smaller explosion had drawn crowds to the area when the car bomb -- apparently a taxi -- exploded in front of a building containing shops selling televisions and satellite dishes -- all forbidden during hardline Taliban rule. The second floor of the building housed a small hotel.

Police sealed off the area, but emergency vehicles could be seen rushing injured to hospitals. Some dazed victims could be seen being led away, their clothing ripped and covered in blood.

Five or six vehicles were destroyed, windows shattered and doors of shops ripped off their hinges.

"This bomb was inside a taxi," said police spokesman Dul Aqa. "It was a very, very strong explosion. We can't say exactly who was behind it but we know the last bombs were Al Qaeda and Gulbuddin [Hekmatyar]."

Hekmatyar, a former military commander, prime minister and president, issued a call for jihad, or holy war, this week to drive U.S. and foreign troops including international peacekeepers from Afghanistan. Some officials have speculated that he may have formed an alliance with remaining Al Qaeda and Taliban leaders, although no clear evidence of this has surfaced.

The blast occurred in one of the most congested areas of the city on a day when many residents do their shopping before Friday's Muslim prayer day. One shopper, Haji Abdul Aroof, said he saw four bodies lying in the street.

"We came to see what was happening when the second bomb went off," he said. "There was a powerful explosion and we all ran."

Thirty-four people were taken to Jamhuriat Hospital, but the hospital lacked facilities to handle broken bones and other serious injuries. The wounded were transferred to the Italian Emergency Hospital and the Wazir Akbar Khan Hospital, doctors said.

At the Italian hospital, staff posted lists with the names of 42 wounded. Staff members said about 65 people had been brought to the hospital but some of the most seriously wounded could not be identified.

Crowds of worried family and friends were pushing and shoving to get a look at the list.

Several main roads in the city were blocked and additional police and soldiers, armed with rocket launchers and automatic weapons, took positions at strategic points in the capital.

The blast was the most serious in a string of bombings that have occurred in the Afghan capital since Aug. 15 when a small blast shattered windows at the Ministry of Telecommunications.

Previous bombings had been small, causing few casualties and relatively little damage.

Officials have been unable to pin down who has been behind the blasts, though suspicions have focused on Al Qaeda elements or Hekmatyar.

During the war against Soviet forces in Afghanistan in the 1980s, Hekmatyar was considered a U.S. ally and one of the strongest of the anti-communist commanders, with heavy backing from Pakistan.

He was named the prime minister in the first Islamic transitional government that followed the end of communist rule in Afghanistan in 1992. But instead he engaged in a bitter feud with his arch rival, Ahmed Shah Massood, killed a year ago by suicide bombers. From 1992 to 1996 Massood and Hekmatyar and their respective allies engaged in brutal fighting that killed 50,000 people in the capital, most of them civilians.

Hekmatyar and Massood finally made peace in the summer of 1996 but by September the Taliban had taken control. Hekmatyar fled to Iran rather than take refuge in the Panjshir Valley with Massood and the northern alliance.

Since the collapse of the Taliban, Hekmatyar has been expelled from Iran. His whereabouts are not known but he is believed to be in eastern Afghanistan. Just a couple of days ago he sent an audio cassette with a warning to the U.S. special forces and to the international peacekeepers in Kabul. He urged the faithful to wage a holy war against them and warned them to leave the country.

This was his second warning.