A video showing London Tube bomber Shehzad Tanweer has been aired on al-Jazeera television.
Tanweer, from Leeds, killed seven people on a train at Aldgate during the attacks on 7 July 2005.
He says on the video: "What you have witnessed now is only the beginning of a string of attacks that will continue and become stronger."
Police said the release of the video on the eve of the bombings' anniversary was designed to cause "maximum hurt".
Tanweer says in a Yorkshire accent on the film that attacks will continue "until you pull your forces out of Afghanistan and Iraq".
It is believed a third man who features in the 31-minute video refers to the Forest Gate raid of 2 June - proving that the video was collated by al-Qaeda in the last five weeks, according to BBC security correspondent Frank Gardner.
The video, the release of which was announced on an Islamist website, includes a statement from Ayman al-Zawahri, al-Qaeda's second in command, and American Adam Gadahn, also known as Azzam al-Amriki.
Gadahn is believed by US authorities to be running al-Qaeda's propaganda operation.
The footage includes people igniting explosives and armed with guns, as well as images of an unidentified man circling points on a map of London.
It is very similar to a video of fellow bomber Mohammad Sidique Khan, released in September 2005.
Both bombers were dressed in a similar way, including headdresses, and the videos had the same "al-Sahab" logo, said to be a signature of al-Qaeda recordings.
The video is likely to add weight to the theory that al-Qaeda was behind the London bombings, Frank Gardner said.
The prime minister's official spokesman said Downing Street would not be giving a reaction to the video.
He said: "I think we want the attention to focus on the quiet reflection of the nation as a whole and I don't think anything should be allowed to get in the way of that."
Scotland Yard's Assistant Commissioner Andy Hayman said police were aware of the video and that it would form part of their investigation.
"There can be no doubt that the release of the video at this time can only cause maximum hurt and distress to the families and friends of those who died on 7/7 and the hundreds of people who were injured in the terrorist attacks.
"We are sure that the overwhelming majority of all communities are united in condemning any attempt to justify last year's terrorist attacks in London," he went on.
Tanweer killed seven people on a train at Aldgate
A spokesman for the Leeds Muslim Forum, Arshad Chaudhry, said it was very sad that the tape had been released at the time of the anniversary of the bombings, which he called "tragic" for those affected.
"The Muslim community has been very badly affected by [the bombings], particularly in the Beeston and Leeds area," Mr Chaudhry said.
"This will just make life even more difficult, with all the media attention and the rest of the community pointing the finger, which is not justified."
Tanweer's family were made aware of the video by police on Thursday morning.
They refused to comment on it but a family friend, Irshad Hussain, said the tape's release had been timed to cause maximum damage.
He said: "It shows you what evil people are out there trying to cause anger and frustration.
"It is wrong what he [Tanweer] is saying and everybody knows that, but, unfortunately, there are people who may listen to what he says."
Mr Hussain said Tanweer's parents would be "devastated" to see their son in the video.
"They are still trying to come to terms with what has happened and to see their son on screen will be torture," he said.