German police on Tuesday detained a 17-year-old militant who a spokesman for the interior ministry in the state of Brandenburg said was a Syrian planning a suicide attack in Berlin, citing a report by the German news agency DPA.

"I can confirm that," the spokesman said, referring to the report.

However, Brandenburg police said they had not yet found evidence that the suspect, who was arrested in the Uckermark region north-east of Berlin, was planning an attack.

"The Syrian nationality and concrete attack plans could not so far be confirmed. The investigations continue," Brandenburg police tweeted.

"According to evidence, he joined Jihad and said goodbye to family members," they added, referring to the term for Islamic holy war.

Memories are still fresh in Germany of the Berlin Christmas market attack last December, in which 12 people were killed by a failed asylum seeker who had pledged allegiance to Islamic State.

Last Wednesday, police arrested four suspected Islamists in dawn raids in Berlin as the German capital geared up for a long weekend of mass gatherings, capped by a joint appearance by Chancellor Angela Merkel and former US president Barack Obama.