Al-Jazeera on Thursday aired snippets of a video tape attributed to al Qaeda, in which it said the network's number two Ayman al-Zawahiri claims responsibility for the July 7 London bombings.
The Qatar-based Arab television station said the video, more of which was to be broadcast later in the evening, also showed footage of one of the bombers, Mohammad Siddique Khan, outlining the reasons for his action.
Al-Zawahiri describes the rush-hour bombings on underground trains and a bus as a "slap for the policy" of British Prime Minister Tony Blair, the channel said.
Al-Jazeera aired footage of a turbaned man alleged to be Siddique and said he explained the reasons for his action.
He blamed Western citizens for the bombings in London and last year in Madrid, as well as for the September 11, 2001 attacks on the United States, "because they elect governments which perpetrate crimes against humanity."
Siddique, a 30-year-old British national of Pakistani origin, was named as one of the four suicide bombers who killed 52 people in co-ordinated attacks in London.
Zawahiri, for his part, "described the bombings as a slap to the policy of... Blair and said these operations have taken the battle to the enemy's land," Al-Jazeera said.
He also slammed Europeans for spurning a truce offer by al Qaeda chief Osama bin Laden. The news channel, which often carries exclusive video and audiotapes, attributed to al Qaeda, showed Zawahiri with an automatic rifle next to him. The television said it would broadcast more of the videotape at around 2000 GMT.