German Justice Minister Heiko Maas has condemned anti-migrant violence in the eastern-German town of Heidenau.

We must never tolerate people in our country being threatened or attacked.

“We must never tolerate people in our country being threatened or attacked,” he said in a statement. “We must pursue this with the full force of the rule of law.”

What started as a peaceful demonstration later turned violent as bottles and stones were thrown at bus loads of migrants attempting to enter the town.

Media reports suggest scuffles broke out when a group of far-right radicals joined the several-hundred-strong crowd calmly marching against the expected arrivals.

The group is then said to have started chanting xenophobic slogans before clashes began in which 31 police officers were reported injured.

The number of arrests made has not been released.

Tear gas was used to disperse the crowds and some of the buses reached their destination, local media quotes the police as saying.

Of an expected 250 migrants, 93 arrived between Friday and Saturday (August 21-22), with more due over the weekend.

Migrant arrivals are putting increasing strain on Germany. According to Eurostat figures, in the first quarter of 2015 it received 73,000 asylum requests, which represents an increase of a 120 percent on the same period last year.