Rival protests over a murder in the east German city of Chemnitz have ended with several people injured as objects were hurled by both sides, police say.

Far-right activists had gathered in the centre for a second day as a Syrian and an Iraqi remained under arrest on suspicion of Sunday’s deadly stabbing.

Anti-Nazi activists rallied just metres away, accusing the far right of using the death for political ends.

Injuries were caused when protesters on both sides threw objects, police say.

German Chancellor Angela Merkel had warned that “vigilante justice” would not be tolerated.

Police warned masked demonstrators who were picking up stones in the city 190km (118 miles) south of Berlin that their actions were being filmed.

Earlier, the authorities said police were investigating alleged assaults on an Afghan, a Syrian and a Bulgarian during the unrest that broke out on Sunday.

Reports have included mentions of protesters chasing foreigners, though there are few details, and police have appealed for witnesses to the assaults to hand over any video they may have recorded.

Initially, about 100 people gathered on Sunday for a rally which passed off without incident, AFP news agency reports.

However, some 800 people later gathered at the Karl Marx monument, a focal point in the centre of Chemnitz.

The monument is a throwback to the city’s days as a model socialist city in the former German Democratic Republic, when it was renamed Karl-Marx-Stadt.

It appears that such a large, angry demonstration took police by surprise.

Freelance journalist Johannes Grunert told Spiegel Online he had witnessed some protesters using bottles to attack people “who did not look German”.

Pegida, the far-right street movement, called for a new demonstration on Monday afternoon, while an MP from the far-right political party AfD, Markus Frohnmaier, tweeted: “If the state is no longer to protect citizens then people take to the streets and protect themselves. It’s as simple as that!”

“Today it’s a citizen’s duty to stop the lethal ‘knife migration’!” he wrote, alluding to the influx of migrants in recent years. “It could have targeted your father, son or brother!”

As the heap of wreaths and candles at the spot where the murder occurred grew larger on Monday evening, right-wing demonstrators massed at the Marx monument, and counter-demonstrators gathered close by.

Police reported Hitler salutes being thrown among the right-wing crowd, where anti-immigration placards can be seen with messages like “Stop the asylum flood”.