BERLIN: A German Islamist has threatened to attack Berlin this summer and kill Chancellor Angela Merkel in a video posted on the Internet, a newspaper reported on Saturday.

A spokesman for Germany's intelligence service, the Office for the Protection of the Constitution, confirmed its agents had seen such a video.

"This is an Islamist battle song. It is known to the security services and is being evaluated," said the spokesman.

Die Welt newspaper reported that a three-minute video had surfaced on the Internet with a German Islamist calling himself Abu Azzam, believed to be a radical Salafist who moved to Egypt last year.

"Looking back at an Arab spring, we are looking forward to a European summer," said Abu Azzam in the video, according to the newspaper.

"Osama, wait for us... We want to see Obama and Merkel dead," he was quoted as saying, adding that Germany's Reichstag parliament building would be subject to attacks like those on New York's World Trade Center in 2001.

German authorities have stepped up surveillance of Salafist groups who espouse a radical version of Islam. Germany is home to roughly 4,000 Salafists, a tiny proportion of the total Muslim population of about four million.

Germany's involvement in the NATO mission in Afghanistan has led to fears of an attack on German soil. Berlin is also supplying military transport planes to fly West African troops to Mali to help French and Malian forces fighting Islamist rebels.