German police have arrested a 19-year-old Syrian man suspected of planning an Islamist bomb attack in the country using powerful explosives.

Several apartments were also searched in the town of Scherwin, which is north of Berlin.

The man, identified only as Yamen A, is suspected of having "planned and already concretely prepared an Islamist-motivated attack in Germany using very powerful explosives," the federal prosecutor's office said in a statement.

"It has not yet been established whether the suspect already had a target in mind or not," it said.

Authorities did not say when the teenager arrived in Germany, but did say there were no indications that he was a member of a terrorist organisation.

German police have been on high alert to the threat of Islamist attacks, particularly after a truck rampage claimed by the Islamic State group killed 12 people in Berlin last December.

A report published in September found that Berlin authorities had missed several opportunities to arrest and deport the driver, Tunisian asylum seeker Anis Amri.

Chancellor Angela Merkel, who is trying to form a new coalition government after elections last month, has come under fire for allowing more than one million people to enter Germany over the past two years - many of them refugees from Syria.

Her 'open door' refugee policy saw her conservatives lose support in the election to the anti-immigration Alternative for Germany (AfD), which won seats in the national parliament for the first time.