Britain has thwarted attempted terrorist attacks in the last few weeks and faces the continued threat of a repeat of the deadly July 7 London [Images] bombings, the country's top police officer said.

Ian Blair, commissioner of London's Metropolitan Police, said the force needed greater powers to cope with "a new reality" in the wake of the attacks on the capital.

• London Blasts

"The sky is dark," Blair wrote in an article for the Sun newspaper Wednesday. "Intelligence exists to suggest that other groups will attempt to attack Britain in the coming months." He gave no details of the past or future threats. A London police spokesman declined to comment.

Blair's message came a day after a memorial service for the 52 people killed when four young Britons detonated bombs on three trains and a bus on July 7. A second wave of bombings failed two weeks later when four devices failed to explode.

The attacks prompted the British government to propose new anti-terrorism laws and led to heightened security measures across Britain.

Police chief Blair said he needed new powers to detain suspects without trial for longer than allowed under existing legislation.

The global reach of terrorist investigations, use of encrypted computers and the dangers of searching houses, which may contain explosives mean inquiries are taking longer, he said.

"It is the united view of police chiefs that an extension of detention to 90 days is necessary if we are to defeat those planning further terrorist carnage," he wrote in the Sun.

"It is not a power we wish to use frequently. We have no interest in making Britain a police state," he said.