A second night of air strikes was unleashed against Afghanistan as Tony Blair warned last night that the US and its allies in the war against terrorism were in for a "long haul" struggle.

With anti-aircraft fire reported again over the Afghan capital Kabul, the Prime Minister confirmed to a sombre House of Commons that new attacks against Osama bin Laden's al Qaida terrorist network and their Taliban hosts were under way.

"We are in this for the long haul. Even when al Qaida is dealt with, the job is not over. The network of international terrorism is not confined to it," he told MPs recalled to Westminster for a third time since the September 11 atrocities.

"We will continue to act, with steadfast resolve, to see this struggle through to the end and to the victory that would mark the victory not of revenge, but of justice over the evil of terrorism."

Unlike Sunday night, when Royal Navy nuclear powered submarines fired Tomahawk Cruise missiles at an al Qaida training camp, no British forces were thought to be involved in last night's action.

Chairman of the US Joint Chiefs of Staff, Air Force General Richard Myers, said the operation was exclusively American "to the best of my knowledge".

A total of 20 US aircraft, ten of them B1 and B2 bombers, and ten carrier-launched fighter-bombers, were in action, while Tomahawk Cruise missiles had been launched from US warships, he said.

Power was cut in Kabul soon after the latest barrage began, while Taliban officials said that other strikes were taking place at the movement's stronghold in Kandahar.

Mr Blair said initial indications were that the first night's operations were successful in achieving their objective of "destroying and degrading" al Qaida's network and the Taliban's military infrastructure.

"In time, they will be supported by other actions, again carefully targeted on the military network of the enemy," he said.

As news of the attacks were coming through, the US formally notified the UN that in future its counter-terrorist strikes could be extended beyond Afghanistan.

Senior officials said that a legal document sent to the Security Council had said the attacks had been an act of self defence under the UN Charter and reserved the right to extend strikes to other countries harbouring terrorist cells.

Earlier, Defence Secretary Geoff Hoon said 30 targets had been attacked by warplanes and Cruise missiles during Sunday night's onslaught, including air defences, airfields and garrisons as well as al Qaida's camps.

Mr Hoon confirmed that plans were being drawn up to follow up the attacks by sending in ground forces - including the possible use of British troops.

However he warned that if the Taliban regime collapsed and Afghanistan descended into civil war it may be too dangerous to deploy land forces in the country.