KABUL (Reuters) - U.S. aircraft have attacked Kabul and other Afghan cities, dropping at least four bombs or missiles on the capital near the Defence Ministry, witnesses have said.

"I could hear the planes and then there were at least four loud explosions," said Reuters correspondent in Kabul Sayed Salahuddin.

"A black plume of smoke is rising, it seemed to be very big," he said.

Witnesses said bombs or rockets appeared to land near the city centre just as Kabul residents were preparing to settle down for the night on Sunday.

One big blast struck near the Defence Ministry, south of the Presidential palace.

Electricity was cut almost immediately, although it was not clear if this was a result of a strike or a defensive measure.

Witnesses said Taliban anti-aircraft guns across the city began firing into the night sky.

President George W. Bush said the raids were aimed at military installations of Afghanistan's ruling Taliban and guerrilla camps of the al Qaeda network led by Osama bin Laden, blamed for the September 11 attacks on New York and Washington.

British Prime Minister Tony Blair said British forces also took part.

Taliban Ambassador to Pakistan Mullah Abdul Salam Zaeef told Reuters that he had heard via telephone that the southern city of Kandahar, headquarters of the ruling Taliban, was also under attack.

A major command base at the airport in Kandahar, stronghold of Taliban leader Mullah Mohammad Omar and the chief protector of Osama bin Laden, had been destroyed, CNN said.

CNN said residents were fleeing the city. The channel said the eastern city of Jalalabad had also come under attack.

The U.S. has been demanding that the Taliban hand over bin Laden and threatening strikes against Afghanistan since the September 11 attacks.