Travellers in Europe given 'high risk' warning of terror attacks

The Foreign Office warned that there was a "high threat" of attacks in countries including France and Germany, rather than the "general threat" previously identified.

Meanwhile, the State Department issued guidance urging Americans to be vigilant when visiting Europe, highlighting the "potential for terrorists to attack public transportation systems and other tourist infrastructure".

The heightened warnings came after British intelligence officials intercepted a credible plot linked to terror group al-Qaida last week.

The planned attack would reportedly have been similar to the deadly commando–style raids in Mumbai, India, two years ago, with cities in France and Germany also targeted at the same time.

Pakistani and Western intelligence officials also said last night that dozens of Muslim militants with European citizenship are believed to be hiding out in the lawless tribal area of north western Pakistan, training for missions that could include terror attacks in European capitals,

A senior official of Pakistan's Inter-Services Intelligence agency said there were believed to be "several dozen" people with European citizenship –many of Pakistani origin – among the Islamic extremists operating in the lawless border area.

The official, who spoke on condition of anonymity, said foreigners in the area also include Chechens, Uzbeks, Arabs and Turks, one of whom was a former F-16 pilot in the Turkish air force.

On Tuesday night the Eiffel Tower in Paris was evacuated following a bomb threat called in from a phone booth. It was the second such alert at the tower in two weeks. A search by bomb experts found nothing unusual, and the tower was reopened within hours.

On Friday, Sweden announced it has raised its threat alert to the highest level ever because of an increased threat of terror attacks.

There has been speculation that terror leader Osama bin Laden could be masterminding the latest plots personally.

The Foreign Office advice now states: "Like other large European countries, the French/German authorities continue to consider that there is a high threat of terrorism.

"Attacks could be indiscriminate, including in places frequented by expatriates and foreign travellers."

Home Secretary Theresa May urged the British public to report any suspicious activity to help police and security services disrupt the terrorists.

"The first and most important duty of this government is the protection and security of the British people and visitors to the UK," Mrs May said.

She added that the UK was working closely with the US on counter-terrorism, and its new guidance was "consistent with our assessment".

The US State Department stopped short of recommending that citizens stay away from high-profile sites in Europe – as was thought to have been under consideration before.

Instead the department said: "US citizens should take every precaution to be aware of their surroundings and to adopt appropriate safety measures to protect themselves when travelling."