Interior minister says country has concrete indications that militants are planning attacks for this month

Security at German airports, railway stations and major tourist attractions was heightened yesterday after the government said it had received concrete warnings that an Islamist terror cell was planning to launch attacks across the country towards the end of this month.

In city centres, traffic ground to a halt as police imposed emergency controls, while the number of armed security personnel, particularly at airports, was significantly increased as travellers were warned to be vigilant.

"The security situation in Germany has become more serious," said the interior minister, Thomas de Maizi è re, in a statement.

"We have concrete indications of a series of attacks planned for the end of November."

According to senior security forces, Germany's federal criminal police are investigating information that a terror cell consisting of four Islamists from India and others from Pakistan is either planning to travel to Germany or is already operating there. The names of the suspects are known to officials.

De Maizi è re added, in an appeal for calm, that Germany would show its strengths: "We won't be fazed by this."

The warnings follow a recent security scare over parcel bombs sent from Yemen to the US, one of which went through a German airport before it was intercepted in the UK. The explosives were hidden in printer cartridges.

De Maizi è re made it clear yesterday that the new warning was separate from previous ones, but had come as a direct result of the Yemen incident, "in the form of a warning from an international partner," he said, without naming names.

The Yemen parcel bomb plot, he added, had highlighted "the adaptability and persistence of terrorists in pursuing their aims", and had shown the "reliability of some leads".

He said German police, working together "with people from the Islamic area, confirm independently the persistent efforts of Islamic groups to carry out attacks in Germany".

Security at potential target sites such as airports and stations would be increased until further notice, he said, adding that while there were reasons for concern there were "no reasons for hysteria".

Germany has long been considered a target for militants linked to al-Qaida because of the more than 4,500 military personnel it has based in Afghanistan, and because of its role as the financial powerhouse of Europe.

Der Spiegel called the warning a "psycho war against Germany", and said the country had to prepare for the fact that, although it had so far escaped an attack, it could be about to join the list of victims of al-Qaida strikes. Warnings had been received before the attacks in Madrid in 2004, London in 2005 and Mumbai in 2008, but to no avail, it said.