THESSALONIKI — Authorities in Greece promised Monday to toughen rules governing soccer supporters’ associations in the wake of a fatal attack last week on a 19-year-old man who was stabbed and severely beaten by a gang of youths in the northern city of Thessaloniki.

Nine people have been arrested in connection with the Feb. 1 attack in which Thessaloniki resident Alkis Kambanos was killed and two others were injured. Arrest warrants have been issued for two others.

The attackers were reportedly carrying wooden bats, metal bars, a knife, and the curved-bladed reaping hook that was used to stab Kambanos.

The killing has drawn strong condemnation from political leaders. The victim was a fan of soccer club Aris, and his attackers were allegedly supporters of rival PAOK.

“How can this happen over a soccer team?” the murdered man’s father, Aristides Kambanos said in an interview with state-run television, his voice trembling as he sat holding hands with his wife Melina.

“This is something that must be healed. I want this to unite the city. (Thessaloniki) was where I was born and I think it’s the most beautiful city in the world.”

Government spokesman Giannis Oikonomou said tougher penalties and sentencing guidelines for violent fans would be included in a sports bill that will be submitted to parliament next month. It will also include new operating rules for supporters’ club that are often used to stage attacks.

“We will confront violent fans. It is our duty to society and especially to the younger generation, but also to our healthy sports community and the millions of good fans in our country,” Oikonomou told reporters.

One of the suspects has been charged with murder, while the eight others appeared in court Monday. They were led into the building under heavy police protection to appear before a public prosecutor.

In the wake of the slaying, police raided multiple soccer fan clubs in Thessaloniki and the Greek capital, Athens. Several weapons were confiscated. Police consider these places venues where attacks on rival club fans are organized and, often, drug sales take place.

The vice president of the European Union’s executive Commission, Margaritis Schinas, who is from Thessaloniki, visited the scene of the killing over the weekend with flowers, and tributes have been left by soccer fans.

“The violence, fanaticism and hatred of the few will not break us,” Schinas wrote on Twitter. “Those of us who love and serve sports are the many and are stronger.”