DAESH posted pictures on the Internet calling on German Muslims to launch Brussels-style attacks in Germany, singling out Chancellor Angela Merkel's offices and the Cologne Bonn Airport as targets, the SITE intelligence group reported.

Western Europe is on high security alert after last week's DAESH suicide bombings in the Belgian capital that killed 32 people at its airport and in a metro station. On Wednesday, France said it was investigating a man on suspicion of planning an imminent act of "extreme violence."

The images and graphics used by DAESH, widely published by German media on Thursday, included slogans in German inciting Muslims to commit violence against the "enemy of Allah."

Germany's BKA federal police, who monitor suspected militants with German passports returning from stints fighting in Syria and Iraq, said it knew of the images but that their publication did not necessitate extra security measures. "We are aware of this material and our experts are checking it," a BKA spokeswoman said. "It is clear that Germany is the focus of international terrorism and that attacks could happen, but this material doesn't change our security assessment."

Federal Police Chief Holger Muench said after the March 22 attacks in Brussels that DAESH appeared eager to conduct further "spectacular" attacks in Europe as it was suffering setbacks on battlefields in Iraq and Syria.

One of the disseminated DAESH images features a militant in combat fatigues standing in a field and gazing at the Cologne Bonn Airport with a caption reading: "What your brothers in Belgium were able to do, you can do too." Another shows the German chancellery building in Berlin on fire with a DAESH fighter and a tank standing outside the structure. The headline reads: "Germany is a battlefield."

Germany joined the United States-led air campaign against DAESH in Syria last year though limiting its role to reconnaissance and refueling missions after the extremist group killed 130 people in shooting and bombing attacks in Paris.

A third graphic featured a military jet, which German media identified as a Tornado used by the German air force, against the backdrop of a mountainous area juxtaposed with the bloodied faces of women and children – apparently meant to represent civilians who DAESH says have been killed by airstrikes on areas it controls.

The caption under the image says: "Will you continue to grieve or will you finally act?" All five pictures circulated on social media on Wednesday bore the logo of Furat Media, a DAESH affiliate, according to SITE.

German media also published a DAESH video celebrating the attacks in Brussels that featured a three-second shot of Frankfurt Airport, apparently taken from German television news footage. The BKA spokeswoman said police were aware of that video as well and current security measures were sufficient.

Security in Europe faces serious questions after the extremist attacks that killed 32 people in Brussels as reports surfaced indicating that Turkey had warned Belgium about one of the attackers and two additional suspects are on the U.S. terror watch list. Last week, President Recep Tayyip Erdoğan lashed out at European leaders who missed opportunities to prevent terror attacks even though Turkey had previously notified the Belgian authorities and deported one of the Brussels terrorists.

After the attacks, European countries increased security measures and life in Belgium and Europe has been profoundly affected by the attacks. Thousands of soldiers were deployed in the streets, the airport still remains closed, several tube stations are not open and a friendly soccer match between Belgium and Portugal was called off. The attacks also rekindled the debate about European security cooperation and police methods.