Intelligence agencies have disrupted an Al-Qaeda-linked plot to launch terror attacks in Britain, France and Germany, a report said, citing intelligence sources.

Militants based in Pakistan planned simultaneous strikes in London and major cities in France and Germany, Britain's Sky News television reported Tuesday, adding the plan was advanced but the attacks were not imminent.

Spy agencies had for some time been tracking the militants who were planning the attack, according to Sky.

The attacks would have been similar to commando-style raids carried out in Mumbai in 2008, intelligence sources were cited as telling the broadcaster.

The plot in Europe was uncovered after intelligence-sharing between London, France, Germany and the United States, said Sky.

The report of the foiled plot came on the same day the Eiffel Tower in Paris was evacuated following a bomb threat for the second time in a month and amid official warnings in France of an imminent terrorist attack.

When investigators discovered the plan, the US military began helping its European allies track down the organisers in Pakistan, which explains the increase in drone attacks in the country in recent weeks, said Sky.

"I am led to believe a number of these attacks were designed against the leadership of this particular plot," said Sky's foreign affairs editor Tim Marshall.

He added the plot "had an Al-Qaeda and possibly some sort of Taliban connection projecting into Europe."

The Wall Street Journal meanwhile reported Tuesday that the CIA had stepped up drone attacks against militants in Pakistan's tribal areas to try to foil a suspected terror plot against European targets.

The Journal, which cited current and former officials, said the exact nature of the plot could not be learned but it was believed to target multiple countries, including Britain, France and Germany.

Pakistani security officials have reported around 20 drone strikes in Pakistan's tribal belt along the Afghan border this month, the latest on Monday killing four militants.

A top US security official last week said "increased activity" by terror groups signaled a heightened threat against Western countries, including European states.

"We are all seeing increased activity by a more diverse set of groups and a more diverse set of threats," Homeland Security Secretary Janet Napolitano told a US Senate hearing asked about warnings in Europe of a growing terror threat.

She added the threat was "directed at the West generally" and she would be discussing the issue with her European counterparts.

In Paris, the all clear was given late Tuesday following the evacuation of the Eiffel Tower, sparked by a phone call to the operator of the tower at 1640 GMT warning of a bomb.

On Monday, a major Paris train station was evacuated after a bomb alert that proved to be a false alarm.