British intelligence agencies warned of a possible terrorist attack on the London underground more than two years before the July 7 bombings, documents claimed.

The Sunday Times said it has seen leaked documents from 2003 listing Heathrow Airport and the underground in London as likely al Qaeda targets.

The paper claims that information presented to the Joint Intelligence Committee came partly from the interrogation of Khalid Sheikh Mohammed, who was arrested in Pakistan in March 2003.

Suicide bombs on three underground trains and a bus on July 7 killed 52 innocent people and injured 700 others.

One of the four British bombers, Mohammed Sidique Khan, recorded a video before his death, in which he urged fellow British Muslims to join a 'holy war'.

Source: Xinhua