German police have arrested a teenage asylum seeker suspected of planning a suicide attack in Berlin, Brandenburg state officials say.
The suspect, 17, was arrested in the Uckermark district, Interior Minister Karl-Heinz Schröter announced. But Brandenburg police say they have not confirmed reports that the teen, who entered Germany in 2015, is Syrian and was definitely planning an attack.
In December, a jihadist killed 12 people with a lorry in Berlin.
That attack on a Christmas market by Anis Amri, a Tunisian, put security services under intense scrutiny because of the way in which the attacker, who was later shot dead by police in Italy, evaded their surveillance and crossed European borders undetected.
Special forces arrested the teenager after police received a tip-off, Brandenburg police tweeted (in German). He had sent a message to his family saying farewell and that he was joining the "jihad", the police said.
The message was sent via WhatsApp in the past week and Brandenburg authorities received the tip-off late on Monday from two other German states, a police spokesman told the Associated Press (AP).
The Brandenburg interior ministry said the suspect was Syrian but police tweeted that neither the "Syrian nationality" nor "concrete attack plans" could yet be confirmed, and that investigations continued.
Investigators are looking into whether the suspect may have falsely registered as a Syrian, police spokesman Torsten Herbst told the AP.
The suspect had been living in a home for unaccompanied underage refugees in Uckermark, north-east of Berlin, since 2016 and had never before come to the attention of police.
He is currently being questioned and the home is being searched by the state criminal investigation office, Brandenburg police said.
Details of the alleged plot cannot be released due to police operations, which are ongoing, the police added.
Some 280,000 asylum seekers arrived in Germany last year, a drop of more than 600,000 compared to 2015.
Chancellor Angela Merkel's decision to temporarily open the country's borders at the height of the European migrant crisis divided opinion and immigration is an important political issue ahead of the parliamentary election later this year.
Mrs Merkel recently moved to try and ramp up deportations of failed asylum seekers.
Tunisia had refused to take back Anis Amri after his asylum bid was rejected and pressure has increased on Mrs Merkel's government since the December attack. In April, a 16-year-old Syrian refugee was convicted in western Germany for planning a bomb attack and sentenced to two years in a youth prison. The judges in Cologne said the plot was at a very early stage and did not yet pose any threat to the public.