LONDON, England (CNN) -- A previously unknown group calling itself the "Secret Organization group al Qaeda Organization in Europe" released a statement Thursday claiming responsibility for the subway and bus bombings in London earlier in the day.
CNN could not confirm the authenticity of the statement, which was posted on a Web site connected to Islamic radicals.
Metropolitan Police Deputy Assistant Commissioner Brian Paddick said authorities had received no direct claim of responsibility, but investigators were aware of the Web site claim.
"We will be looking into that as well as any other leads, but at the moment we don't know if that's a genuine claim or not," he said.
The statement said Islam and "Arabism" could "receive the glad tidings."
"It is time of revenge against the crusader and Zionist British government has come in response to the massacres committed by Iraq and Afghanistan," said the statement, translated from Arabic by CNN.
In the United States, several military officials said there is no confirmation on responsibility for the attacks, but the working assumption is it may have been conducted by an al Qaeda-related group because of the coordinated nature of the blasts and the near simultaneity of the explosions.
The military officials also said the intelligence community, as expected, will be going back through intelligence reports to see if there are any indicators that may now be apparent.
One senior official told CNN there had been no indications pointing to this type of attack in London.
The claim of responsibility from the group said it had repeatedly warned Britain.
"The mujahedeen heroes have launched a blessed attack in London," the statement said.
"Here is Britain burning now out of fear and horror in its north, south east and west. We have often and repeatedly warned the British government and people."
The statement said the group had carried out the attack after exerting "strenuous efforts ... over a long period of time to guarantee" its success.
"We still warn the governments of Denmark and Italy and all the crusader governments that they will receive the same punishment if they do not withdraw their troops from Iraq and Afghanistan," it said. "We gave the warning, so we should not be blamed."
