Osama bin Laden's al-Qaeda network has strengthened its operations in Europe in recent months and is recruiting militants capable of carrying out new terror attacks, according to German officials.

They are living undetected among us and are prepared to participate in... terror attacks

Manfred Klink

Thousands of al-Qaeda members remain active and "significant numbers" are in Germany, Manfred Klink, head of Germany's federal police, told a meeting of European security experts in Bonn.

Germany became one focus for investigations into the 11 September attacks on the United States, after it emerged that some of the hijackers had been members of an al-Qaeda cell in the country.

The warning comes over a week after the United States administration said further attacks were almost inevitable.

Investigations

Mr Klink told the Bonn meeting that "a network of several thousand fanatic Muslims" was in place in Western Europe.

Atta was based in Hamburg

"We believe that they are living undetected among us and are prepared to participate in strategically planned terror attacks as dictated by their leaders," he said.

Mr Klink said his agency, the Federal Criminal Office, had 30 investigations pending against groups with suspected links to groups advocating terror.

Hans Beth, from Germany's BND intelligence service, said al-Qaeda had been recruiting new militants and improved its efficiency in recent months.

He said Osama bin Laden's organisation had become more decentralised, and less visible - for instance by moving more money without leaving a paper trail.

Three of the 19 suspected hijackers on board the planes which plunged into New York, Washington and Pennsylvania, had been living in Hamburg before the attacks.

Mohammed Atta, Marwan al-Shehhi and Ziad Jarrah were enrolled at the technical university in the city.

Mass destruction

Information received by German intelligence indicates that Osama bin Laden "at least considered" the use of weapons of mass destruction, Mr Beth said.

Cheney: another attack on the US is 'inevitable'

He added that al-Qaeda experimented with poison gas and biological weapons.

The United States administration issued a series of similar warnings earlier this month.

Defence Secretary Donald Rumsfeld said he believed it was "inevitable" that terrorist groups would get their hands on nuclear, biological or chemical weapons.

Secretary of State Colin Powell said he believed terrorists were "trying every way they can to get their hands on weapons of mass destruction".

FBI Director Robert Mueller also warned it was "inevitable" that suicide bombers would strike the US sooner or later, and Mr Cheney has said that more terror attacks on America were "almost certain".