US air strikes on Afghanistan are continuing tonight. There are reports that the Afghan capital, Kabul, has been bombarded for the third time.

One witness told the Reuters news agency: "You could hear a plane, or planes and then there was the reply of guns. It was not clear if more bombs were being dropped. It sounded like some outside the city". Electricity supplies in the city have also been cut.

The Afghan cities of Kandahar and the eastern city of Jalalabad, both Taliban strongholds, have also been raided at least twice.

Twenty-six days after the terrorist attacks on New York's Twin Towers and the Pentagon, the United States and Britain launched air strikes against Afghanistan. President George W Bush said that the action heralded a "sustained, comprehensive and relentless" campaign against terrorism.

It is reported that a Taliban command base in Kandahar has been destroyed. Eyewitnesses in the capital, Kabul, said that the city was rocked by explosions and that power supplies were cut. Military sites in the eastern city of Jalalabad were hit.

The Taliban says that the strikes caused no significant damage - and that Osama bin Laden and the Taliban's spiritual leader, Mullah Mohammed Omar, are still alive.

Bin Laden has given a televised address in which he threatened further attacks against Americans. It is not known when exactly the interview was recorded. The US State Department has warned American citizens to expect retaliation.

The Pentagon confirmed that the assault began with cruise missile attacks against a broad range of Taliban military targets and guerrilla training camps.

A senior Pentagon official said that 15 American bombers, 25 strike aircraft and 50 cruise missiles were used against a number of targets around Afghanistan.

In London, military officials confirmed that British reconnaissance and other aircraft and missile-firing submarines took part in the operation.

American defence officials said that the targets included Taliban air defence and command-and-control sites around Kabul and at an airbase near the Taliban stronghold of Kandahar.

Eyewitnesses said that they saw flashes and heard explosions over Kabul in the first phase of what the United States has said will be a protracted and wide-ranging war against terrorism and the states that support it.

In a televised speech this evening, President Bush said: "On my orders, the United States military has begun strikes against Al Qaeda terrorist training camps and military installations of the Taliban regime in Afghanistan"

"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 Taliban regime," he added.

The British Prime Minister has described the start of attacks on Afghanistan as "a moment of the utmost gravity". Tony Blair confirmed that British forces were involved in the attacks.

The Taliban has condemned the air strikes against Afghanistan saying they were terrorist attacks and has said it will not hand over Osama bin Laden.

Pakistan said Afghanistan's Taliban rulers had brought the US-led military strikes on themselves but hoped the operation would be brief and spare civilians.

"We regret that diplomatic efforts to convince the Taliban leadership to respond to the international demands did not succeed and now military action has started against the Taliban regime," a Foreign Ministry spokesman said.

NATO said it was "not directly involved" in tonight's attacks. A spokesman said essentially this was a mission that involves the United States and Britain right now.