Germany said on Wednesday it had firm evidence Islamist militants were planning attacks in the next two weeks and ordered increased security at potential targets including train stations and airports.
"The security situation in Germany has become more serious," Thomas de Maiziere, Germany's top security official, told a news conference. "We have concrete indications of a series of attacks planned for the end of November."
This is the first time German officials have referred to "concrete" intelligence in reference to a terrorism investigation, NBC News reported.
German public broadcaster ZDF reported Thursday night that German authorities are searching for at least six terrorism suspects, who may already have entered Europe on so-called Schengen visas that allow them free travel across central Europe. According to the report, German authorities have identified the names of the suspects.
Meanwhile, daily newspaper Der Tagesspiegel reported that U.S. intelligence agents informed their German counterparts last week that al-Qaida had sent two to four potential terrorists to Germany and Britain and that the suspected attackers were due to arrive in Germany on Nov. 22.
In the report, Der Tagesspiegel claimed that the suspects were recruited by Pakistan-based Mohammed Ilyas Kashmiri, who is allegedly behind an attack on a popular tourist restaurant in Pune, India, earlier this year.
Germany is soon to open its traditional Christmas markets, and many media outlets identified them as possible targets. But German officials refrained from identifying potential targets.
U.S. counterterrorism officials told NBC News that "this is not business as usual" and stressed that they "will defer to (the) German partners on the details, as this (alert) appears to be based on new information as well as new analysis."
U.S. officials added that "the threat environment has been high in Europe for some time now."
But recent events suggest authorities are dealing "with a new situation," de Maiziere said.
The minister, a senior figure in Chancellor Angela Merkel's center-right government, had initially played down the threat last month when the United States and Britain issued warnings that Germany and France could be targeted by al-Qaida and allied militants.
But earlier this month de Maiziere acknowledged there were "serious indications" of a threat to Europe and the United States.
De Maiziere also pointed to the recent interception of mail bombs sent from Yemen and to German information on "sustained efforts" by Islamic extremist groups to plan attacks in Germany, and to a subsequent tip from another unspecified country about a suspected attack.
That tip arrived after the interception of two mail bombs mailed from Yemen to the United States — one of which transited through a German airport before it was found in Britain.
The Yemen plot points to "the adaptability and the persistence of terrorists in pursuing their aims," and also underlines "the reliability of some leads," de Maiziere said in a statement to reporters, without elaborating.
He said the current risk assessment was comparable to the one before last year's German election — when the country also raised security.
De Maiziere said he is calling on police to beef up security particularly at airports "until further notice."
"There are grounds for concern but not for hysteria," said the minister. "We won't be intimidated by international terror, neither in our way of life, nor our culture or freedom."
Germany has long viewed itself as a potential target because it has 4,590 military personnel stationed in Afghanistan, the third largest contingent of the 150,000-strong international force fighting the Taliban-led insurgency.
And though the country has escaped any major terrorist attacks like the Madrid train bombings of 2004 and the London transit attacks of 2005, at least two major plots have been thwarted or failed before they could be carried out.