Al-Qaida is planning attacks on high-speed trains in Europe and the authorities in Germany have stepped up security on the country's rail system, a German newspaper reported on Monday.

The information about the planned attacks came from the United States' National Security Agency, which apparently intercepted a call between senior al-Qaida members several weeks ago, the mass-circulation daily said.

But the German Interior Ministry said it regularly receives information about such threats and was not planning to increase overall security.

"It is known that Germany, along with other Western states, is a target for jihadist terrorists so we always assess warnings on a case-by-case basis, but we already have a high level of protective measures and we do not plan to step these up at the moment," spokesman Jens Teschke said at a routine government news conference.

The extremist group could plant explosives on trains and tunnels or sabotage tracks and electrical cabling, said Bild, Europe's most widely read daily.

While Germany said its threat level had not changed and Austria said no additional security measures had been taken, a Czech rail official said authorities there had implemented new, unspecified security measures.

Bild said German authorities had tightened security on high-speed Intercity-Express routes and at stations with "invisible measures", including the deployment of plainclothes police officers.

A spokesman for the German federal police said efforts were already commensurate with the "highly dangerous situation both at home and abroad" but said it had alerted its forces.

The attacks on Europe's rail network were a "central topic" of this call, Bild said.

A spokeswoman for German rail operator Deutsche Bahn would not comment on the Bild report, but said the company was always in regular contact with the security authorities over possible threats.

According to US media reports, intelligence services intercepted a conference call earlier this month between al-Qaida leader Ayman al-Zawahiri and more than 20 operatives from across the group's global network.

Earlier this month the US closed around 20 embassies and consulates in the Middle East and Africa after saying it had picked up information through surveillance and other means about unspecified threats.

Germany narrowly avoided an attack in 2006 when two suitcase bombs left on commuter trains in Cologne failed to explode.

The Austrian interior ministry meanwhile said there were "no grounds for concern". While authorities were in contact with their counterparts in neighboring countries, no special security measures had been taken for trains or stations.

The Czech railway, however, said it had beefed up security after the Bild report.

"We took some preventive measures to not be caught by surprise," said Jakub Ptacinsky, spokesman for the SZDC company in charge of Czech railway infrastructure.

"One must underestimate nothing," he told AFP, while refusing to specify the kinds of measures for "tactical reasons".

Reuters-AFP