Mayor Teddy Kollek said Thursday that the first firebomb attack in Jewish west Jerusalem since the Arab uprising began signals a dangerous escalation of anti-Israeli violence.

Arab assailants hurled two firebombs Wednesday at an Israeli bus in west Jerusalem's busy commercial district. Police said there were no casualties.Although stone throwing and firebomb attacks have escalated recently in east Jerusalem, where 135,000 Arabs live, the attack Wednesday was the first time the violence has spread into Jewish west Jerusalem.

Prime Minister Yitzhak Shamir said the firebombing showed that the Arab uprising is a serious threat.