Arab television broadcast footage Thursday of a man who claimed to be one of the four attackers in the July 7 London transit bombings, saying that the violence was motivated by "atrocities" against Muslim people. The al-Jazeera network also aired a tape from al Qaeda's second-in-command asserting that the "glorious raid" in Britain "has moved our battle right to the enemy's doorstep."

"Until you will stop the bombing, gassing, imprisonment and torture of my people, we will not stop this fight," said the man, who identified himself as Mohammed Sidique Khan. Khan, a British Muslim, has been identified by London police as one of the four bombers, who killed themselves and 52 others.

"We are at war, and I am a soldier and now you too will taste the reality of this situation," he said in the video, on which he professed admiration for Osama bin Laden.

The man, who spoke in English, wore a red-and-white head scarf and a dark jacket. British officials said they were aware of the tape but did not comment on its authenticity, the BBC reported.

If the tape turns out to be authentic, it would offer the first direct explanation for the deadliest attack on British soil since World War II. While the tape does not claim that al Qaeda was involved in planning or carrying out the attacks, it suggests that the terrorist network's radical philosophy is inspiring young Muslims to commit violence in response to the policies of the United States and Britain in Iraq and the Middle East.

In the second tape, Ayman Zawahiri, an Egyptian-born surgeon who is bin Laden's right-hand man, calls the London bombings a "slap in the face of the arrogant, crusader British rulers" and "a sip from the glass that the Muslims have been drinking from." As he had in a taped broadcast last month on al-Jazeera, Zawahiri said the London attacks, along with the Sept. 11, 2001, attacks on the United States and the 2004 train bombings in Madrid, were responses to the policies of President Bush and British Prime Minister Tony Blair.

"We have repeated again and again, and here we are warning one more time: All those who took part in the aggression on Iraq, Afghanistan and Palestine, we will respond in kind," Zawahiri says in Arabic on the tape, which carried English subtitles.

British police have identified Khan, 30, a teaching assistant from the city of Leeds, as the eldest of the four suspected July 7 bombers.

Images from closed-circuit television surveillance cameras released by police show Khan and three other young Muslim men meeting in a train station in northern England on the morning of July 7 before splitting up and heading in different directions. They all wore backpacks, which police said were filled with explosives that they detonated on three subway trains and a bus during the morning rush hour.

Seven people died on the train where police say Khan killed himself.

Khan and another of the presumed bombers, Shehzad Tanweer, traveled together to the Pakistani city of Karachi last November, Pakistani officials said. They released photos of Khan and Tanweer taken by immigration authorities. It is unclear what the pair did during their three-month stay, but Pakistani records show that they left on the same flight in early February, the BBC reported.