A Muslim man has been attacked at a mosque in Adelaide's south after refusing to have a political discussion about the Israeli-Palestinian conflict.

The ABC has obtained security vision that shows a Muslim man in his 40s being punched in the face.

Islamic Society of SA president Ahmad Zreika said the worshipper was attending evening prayers around 9:30pm on Friday when a member of the public attended the mosque asking questions about the religion.

"We open our mosque doors every day to the general public in the hope that we can open meaningful dialogue, so that we can work on becoming a more inclusive Australia," Mr Zreika said.

But he said when the worshipper refused to answer questions about the Israeli Palestinian conflict — because he did not have the political insight — the man punched him in the face.

"He asked him, 'What's your opinion about what happened in Jerusalem, are you against it, or with?'" Mr Zreika said.

"The Muslim man says, 'I don't want to be involved in this' and the other man said 'You should have an opinion' and punches him."

Mr Zreika said the man stood about while the Muslim man looked for help.

"After a few minutes the attacker left the mosque and the brothers inside the mosque called the police," he said.

The man was not taken to hospital but was in shock.

"He couldn't understand why the man attacked him just for not expressing an opinion," Mr Zreika said.

Police searching for suspect

Police said they were investigating an assault that occurred at a Park Holme mosque.

A severed pig head was thrown at the mosque earlier this year. ( Supplied )

They said the victim was punched in the face and sustained facial injuries, for which he was treated at the scene by paramedics.

Police said the suspect was not known to the victim and they were making inquiries to find him.

It was the third attack on the mosque this year.

"You are coming a worship place ... a peaceful environment ... it's really unacceptable," Mr Zreika said.

One month ago a severed pig head was thrown at the mosque, while earlier this year rubbish, eggs and a baseball ball were thrown at a window.

"We didn't inform the public because at the time we thought maybe it's just kids," Mr Zreika said.

"But when there's violence happening, we decided to inform the community [about] what's going on because it's really unacceptable."

The ABC has contacted the alleged victim for comment.