Intelligence officials have intercepted a credible terror plot against Britain, France, and Germany raising security fears at the Eiffel Tower yesterday, but failing to raise the overall threat level in those countries.
The Eiffel Tower was briefly evacuated yesterday evening after officials received a bomb threat called in from a telephone booth.
It was the second such alert at the monument in two weeks.
The warning came as French officials were put on alert for possible terror attacks.
British officials, too, have been aware of a possible attack but the terror threat warning has not changed from "severe".
"There have been a succession of terror operations we've been dealing with over recent weeks but one to two that have preoccupied us," said one British government official, who spoke on condition of anonymity because of the sensitivity of his work.
"Still, it hasn't been to the degree that we have raised the threat level."
Another official, who spoke on the same terms, would not confirm the plot was "al-Qa'ida inspired" but said there was an "Islamist connection" and that the plots were in an early stage. No other details were given.
Since the September 11 attacks in the United States nine years ago, the terror group has moved outside of Afghanistan and Pakistan to other countries such as Somalia and Yemen.
In Washington, a Western counterterrorism official said some missile strikes in a recent surge of attacks by unmanned US drones in Pakistan were aimed at disrupting suspected terrorist plots aimed at Europe.
It wasn't known whether the drone attacks were related specifically to the plot that European authorities said they had intercepted.
The counterterrorism official said the targeted strikes were aimed at al-Qa'ida and other militant groups arrayed in Pakistan's tribal region near the Afghanistan border. The official spoke on condition of anonymity because the details of the terror plot remain sensitive.
The Obama administration has intensified the use of drone-fired missiles in Pakistan's border area but this month there have been at least 21 attacks, more than double the highest number fired in any other single month.
A suspected US missile strike yesterday killed four militants in northwest Pakistan's South Waziristan region, just across the border from Afghanistan, intelligence officials said. There was no word on the identities of those killed in the attack.
The counterterrorism official, who is familiar with the drone strikes and the details of the Europe terror plots, said yesterday that the missile strikes in Pakistan are "a product of precise intelligence and precise weapons. We've been hitting targets that pose a threat to our troops in Afghanistan and terrorists plotting attacks in South Asia and beyond".
In Paris, French police yesterday closed off the surroundings of the Eiffel Tower, France's most visited monument. Officers pulled red-and-white police tape across a bridge leading over the Seine River to the monument. Officers stood guard.
Bomb experts combed through the 324m tower and found nothing unusual, the Paris police headquarters said. Tourists were let back inside about two hours after the structure was emptied.
Jean Dupeu, a 74-year-old Paris retiree, had planned to go to dinner in the tower.
"It's surely a bad joke," he said of the threat, adding, "Now is not a good time."
National Police Chief Frederic Pechenard said last week that authorities suspect al-Qa'ida's north African branch of plotting a bomb attack on a crowded location in France. His warning came after al-Qa'ida in the Islamic Maghreb, or AQIM, claimed responsibility for the September 16 abduction of five French nationals and two Africans in northern Niger.
The French parliament voted this month to ban burqa-style Islamic veils in France, a subject that has prompted warnings by AQIM.