One big blast struck near the Defence Ministry, south of the Presidential palace. Electricity to the city was cut almost immediately. Other witnesses reported two waves of strikes against a major command base at the airport in Kandahar, stronghold of Taleban leader Mullah Mohammad Omar.
The attack had been under preparation since the September 11 suicide attacks on the United States that destroyed the twin skyscrapers of New York's World Trade Centre and badly damaged the Pentagon outside Washington, killing around 5600 people.
The United States blamed Saudi-born militant Osama bin Laden and his al Qaeda network for the attacks and accused Afghanistan's Taleban rulers of shielding him.
In a televised address from the White House, Mr Bush said the strikes against Afghanistan were carefully targeted at military installations and the United States would air drop food to needy Afghan people to demonstrate that its war was not against them.
"These carefully targeted actions are designed to disrupt the use of Afghanistan as a terrorist base of operations and to attack the military capability of the Taleban regime," Bush said.
The Taleban ambassador to Pakistan, Mullah Abdul Salam Zaeef, said the US strikes on his country were a "terrorist" attack, the Afghan Islamic Press (AIP) said.
"Poor and common Afghans will die, for which America will be responsible. This is an attack on an independent country. We will fight to the last breath," he said.
US defence officials said the night attack began with cruise missiles against a broad range of Taleban military targets and guerrilla training camps.
The $US1 million ($2.48 million) missiles can be fired from US bombers and American and British warships. They are guided to their targets by satellites.
Last month's attacks on the United States transformed Bush from a hesitant leader who came to office in January after an indecisive and disputed election into a commander-in-chief enjoying the backing and approval of the vast majority of Americans.
"We are joined in this operation by our staunch friend, Great Britain," he said, adding that Canada, Australia, Germany and France had also pledged forces as the operation unfolds.
"More than 40 countries in the Middle East, Africa, Europe and across Asia have granted air transit or landing rights. Many more have shared intelligence. We are supported by the collective will of the world," he said.
In declaring the beginning of the military operation, Bush followed in the footsteps of his father, former President George Bush, almost 11 years after his father announced the start of the Gulf War against Iraq.
"Now, the Taleban will pay a price. By destroying camps and disrupting communications, we will make it more difficult for the terror network to train new recruits and co-ordinate their evil plans," Bush said.
He called on Americans and their allies to be patient, saying this war would not be over quickly. Initially, he said, bin Laden and his terror network might be able to burrow deeper in caves and other hiding places.
"Our military action is also designed to clear the way for sustained, comprehensive and relentless operations to drive them out and bring them to justice," Bush said.
The attack came hours after Washington rejected an offer from Afghanistan's Taleban to put bin Laden on trial, a last-ditch attempt to stave off US military action.
Bin Laden, 44, an extremist Islamic militant from a wealthy Saudi family, has been defying US efforts to capture or kill him for years. Since 1996, he has been living under the protection of the Taleban in Afghanistan in a remote mountain redoubt.
He has also been indicted for the deadly 1998 bombings of the US embassies in Dar es Salaam, Tanzania, and Nairobi and was linked to last October's attack on the USS Cole in Aden, Yemen, which killed 17 American servicemen.
A week after the attack on the United States, Bush presented the Taleban with an ultimatum, demanding that they surrender bin Laden and lieutenants in his al Qaeda network, close his training camps, allow international inspections, and release detained aid workers.
He said if they failed to comply, the Taleban would share the fate of the bin Laden network. The Taleban adheres to an extreme, puritanical form of Islam, under which women are not allowed to work, seek education or show their unveiled faces in public.
Afghanistan's opposition Northern Alliance said it had complied with a US request to close its airspace and ground its small fleet of helicopters and fixed-wing planes a few hours before the attack began.
It warned residents of Kabul to stay away from military installations.
The Taleban has been diplomatically isolated and is now almost encircled by hostile military forces as the assault began.
Under intense pressure and with reports mounting of defections by some of its supporters, the Taleban has reacted with a mixture of defiance and attempts at conciliation.
It said an extra 8000 troops were being sent to its northern border with Uzbekistan to join several thousand already there.
"We have deployed our forces there at all important places. This is the question of our self respect and we will never bow before the Americans and will fight to the last," Afghan Islamic Press quoted a Taleban spokesman as saying.
Afghan opposition forces fighting the Taleban said on Sunday they had seized 11 villages in the central province of Ghor and were advancing on the provincial capital Cheghcharan.
An opposition spokesman, Mohammad Habeel, said Taleban defections were partly responsible for the advance in Ghor, which followed reports on Saturday of similar movement in the northern province of Samangan.
"The probability of the fall of Cheghcharan is high," Habeel told Reuters by satellite telephone.
The United States has sent 1000 soldiers to Uzbekistan, which shares a border with Afghanistan, and the Voice of America said the first planes had landed.
US and British aircraft carriers, more than 300 warplanes, ships armed with cruise missiles and special forces troops gathered within striking distance of Afghanistan. Some 30,000 other troops have also been deployed.
In Kabul, scores of people prepared to leave the beleaguered capital, a day after Taleban anti-aircraft guns tried to shoot down a circling spy aircraft.
Security forces in Pakistan's border province of Baluchistan ordered Afghan refugees to move from camps near the airport after intercepting a message threatening to down an airliner.
The United Nations says a quarter of Afghanistan's 24 million population are dependent on food aid, that more than a million people have fled their homes within the war- and drought-ravaged country. The UN estimated that up to 1.5 million more may try to cross into neighbouring countries.
Aid agencies stepped up their pleas for emergency food shipments to the country and Oxfam said between 1 million and 2 million people were already on the road in Afghanistan, trying to reach safety.
- REUTERS
