Arsonists Friday torched the offices of Beitar Jerusalem football club, embroiled in conflict with some of its more racist supporters over the signing of two Muslim footballers from Chechnya, police said.
The attack took place hours after prosecutors on Thursday filed charges against four Beitar supporters accused of racist chants aimed at the Muslim players during a match and at a training session.
"The offices were torched in the early hours of the morning and we have opened an investigation," Jerusalem police spokesman Shmulik Ben Ruby told AFP, adding that no suspects had so far been identified.
The fire caused irreversible damage to the club's collection of memorabilia, said its curator, Meir Harush.
"They burned a room with all the historic objects of Beitar Jerusalem -- pictures, cups, everything in the history of Beitar Jerusalem was in this room and it was burned," Harush told AFP.
Prime Minister Benjamin Netanyahu said in a statement that in light of the Jewish people's historic suffering at the hands of racists, such behaviour by Israelis was "shameful."
"We cannot accept such racist behaviour," he said.
"Those who did this are not fans but criminals in every way," Jerusalem mayor Nir Barkat said in a statement reacting to the arson. "This is an act reminiscent of the behaviour of an organised crime organisation."
Beitar on January 26 announced its acquisition of Zaur Sadaev and Dzhabrail Kadaev, signed from Russian League club Terek Grozny.
The news enraged some of the club's fans, who chanted racist anti-Arab slogans and waved signs reading "Beitar -- pure forever" during a game later that day.
After the match, police arrested three fans for incitement to racism, but Russian-Israeli owner Arkady Gaydamak insisted the signing would go ahead, saying the opposition came from a small minority of supporters.
Beitar Jerusalem have a reputation for attracting a hard core of anti-Arab fans, with many of its supporters adamant the club should never sign an Arab player, even though Muslim footballers have played for Beitar in the past.