A group of young people in eastern Germany threatened three Syrian refugee children with a knife and hit them before chanting right-wing slogans on Thursday evening, police said.
The refugee boys aged five, eight and 11 were getting out of a bus in the eastern town of Sebnitz, around 40 km (25 miles) east of Dresden, when they were attacked, police said in a statement.
A spokeswoman for the police could not confirm the nationality of the attacker, adding that their identity was not yet known.
Police found several young people aged between 15 and 20 near the site of the attack but it is not yet clear if they were the attackers.
Germany, Europe's largest economy, has taken in a total of 1.1 million migrants so far this year and last, upsetting some Germans who feel that their country is being overrun by foreigners with different cultures or religions to their own.
Support for the anti-immigrant Alternative for Germany (AfD) party has surged since last year's migrant influx, particularly in eastern states where unemployment is generally higher than in the west.