An independent organisation promoting worldwide press freedom has called on Greek authorities to investigate the attack on a journalist during a demonstration by far-right supporters at Syntagma Square in Athens on Sunday.

The US-based Committee to Protect Journalists (CPJ), which is made up of about 40 experts around the world who monitor and act on press freedom violations, said German journalist Thomas Jacobi was assaulted by a group of about 10 men during a demonstration against Greek government policy on refugees.

The men approached the journalist and asked him if he was Thomas Jacobi. When he said yes, they knocked him down and beat him for several minutes before a group of journalists intervened. The attackers destroyed Mr Jacobi’s mobile phone and took his recorder. The journalist was taken to hospital and treated for head injuries and was later released.

READ MORE: Golden Dawn are Nazis, plain and simple

According to France 24, Mr Jacobi said the attack had been witnessed by policemen but that they had not intervened.

“They were hitting me for four-and-a-half minutes until some policemen appeared. None stepped in. That’s the most shocking thing,” Mr Jacobi told Proto Thema.

“They attacked me because they recognised me,” he added.

Mr Jacobi had worked with journalist Angelique Kourounis on a 2016 documentary on Greek far-right party Golden Dawn, titled The Golden Dawn: A Personal Affair.

Last year Mr Jacobi and two other journalists were attacked by members of Golden Dawn during a protest in central Athens.

Greek government spokesperson Stelios Petsas condemned the “fascist attack” on Mr Jacobi and said that the authorities were investigating the incident.

The Foreign Press Association of Greece (FPA) called on authorities to take all necessary action to identify the attackers.

“The existence of organised hit squads at the fringes of rallies aiming to intimidate journalists that are not of their liking can’t be tolerated,” said the FPA in a statement.