Osama bin Laden's chief lieutenant praised the July 7 bombings in London in a videotape that also featured a statement from a man who closely resembled one of the bombers. The tape, broadcast on al-Jazeera on Thursday, said al-Qaeda would carry out more attacks.
If proved authentic, the tape would either be evidence of a link between al-Qaeda and the bombings, or an attempt by the group to associate itself with the attacks after the fact. Officials in Britain and the US said they were aware of the tape and were investigating it, but could not comment on its authenticity.
The man resembling one of the British-born bombers, Mohammad Sidique Khan, read what Al-Jazeera described as a testament, somewhat like those recorded by Palestinian suicide bombers for broadcast after an attack. Speaking in a Yorkshire accent, he praised "our beloved sheik, Osama bin Laden," and declared, "We are at war, and I am a soldier and now you too will taste the reality of this situation."
The video included what appeared to be a section showing Ayman al-Zawahiri, al-Qaeda's the second-in-command, speaking of "the blessed London battle."
"Like its glorious predecessors in New York, Washington, and Madrid, this blessed battle has transferred the battle to the enemies' land," al-Zawahiri said, speaking in Arabic.
The two men did not appear together on the tape.
It was not clear when the tape was recorded or why it took so long to be released. It was broadcast exactly eight weeks after the July 7 attack, in which 56 people died, including the four bombers.
British Prime Minister Tony Blair has strenuously resisted the idea that the bombings were inspired by Muslim anger at his decision to commit British troops to the Iraq war alongside US forces.
In the tape, al-Zawahiri referred specifically to the "inferno of Iraq," and said Blair was conducting a "crusader war against Islam."
On July 7 four bombers, Khan, two other British-born men of Pakistani descent and a Briton of Jamaican ancestry, died in attacks on three subway trains and a red double-decker bus.
Two weeks later, four more men attacked similar targets but there were no direct casualties. Three of the main July 21 suspects are under arrest in Britain; a fourth awaits extradition hearings in Rome.
Up until now, investigators had leaned towards the theory that the two sets of bombers were local cells operating separately and without a common mastermind. One of the July 21 suspects has said he and others launched a copycat attack with no intention to cause harm.
The video broadcast on Al-Jazeera was the first purporting to show one of the July 7 bombers offering his reasons for the attack.
"I am going to keep this short and to the point because it's all been said before by far more eloquent people than me," said the man, whom the BBC said identified himself in the tape as Khan. "But our words have no impact upon you. Therefore I'm going to talk to you in a language that you understand. Our words are dead until we give them life with our blood.
"I'm sure by now the media has painted a suitable picture of me. This predictable propaganda machine will naturally try to put a spin on it to suit the government and to scare the masses into conforming to their power and wealth-obsessed agendas."
"Oh, nations of the Christian alliance, we have warned you before. So taste some of what you have made us taste," al-Zawahiri said.