An Alternative for Germany (AfD) politician was injured with a knife in Germany’s southern city of Mannheim, just days after a terror attack in the same city in which a police officer was murdered.

Heinrich Koch, a candidate in the local elections, says he was attacked by Left-wing extremists after he caught them tearing down campaign material for the AfD party in Mannheim.

In a video posted on social media purporting to show the moment of the attack, Mr Koch stops a man carrying AfD placards and what appears to be a Stanley knife. The pair then get into a scuffle and Mr Koch can be heard shouting for the police.

Mr Koch was later taken to hospital where he required stitches for the cuts. A spokesman for the AfD said the perpetrators were “Left-wing extremists”, while German police have not yet given any details about the suspects’ identities.

Mannheimer Morgen, a local newspaper, reported that the alleged knife attacker has already been arrested and that police are seeking two other suspects.

Mr Koch, 62, is a founding member of the AfD’s district association in Mannheim and a former engineer.

Authorities in Mannheim are on high alert after a stabbing rampage last week, in which an Afghan extremist killed a police officer and injured a Right-wing anti-Islam blogger.

The suspect, Sulaiman Ataee, 25, is a married father-of-two who came to Germany as a child refugee 10 years ago, according to German media reports.

He was a successful student who seemed well integrated into German society, but appears to have turned to radicalism shortly after moving to the Mannheim area, sources told Bild newspaper.

German police say they suspect Ataee launched the assault in Mannheim as he wanted to silence critics of Islam. His main target, Michael Stürzenberger, is a controversial figure who was once fined – and then acquitted – for calling Islam a “cancer” in a blog post.

He has also compared the Koran to Adolf Hitler’s rambling autobiography, “Mein Kampf”, and has suggested that all Muslims are terrorists.

Responding to the death of the police officer in last week’s attack, Mr Stürzenberger warned that “political Islam” was sowing violence in Germany.

“My thoughts are with his family and his police colleagues, who could always rely on him, as has been reported. He did his best in Mannheim on Friday,” Mr Stürzenberger said in a post on social media.

“He was the victim of a brutal, ruthless killer who apparently, due to his ideology, saw the police as his enemy. Because they defend the free, democratic constitutional state that he wants to abolish... political Islam is the greatest threat to our security and freedom,” he added.