Israeli security forces clashed with stone-throwing Palestinians in Jerusalem's Old City Monday, and Arab hospital officials said 22 Palestinians were killed.

More than 150 Palestinians were wounded in the violence, considered the worst in the Old City since the Palestinian uprising broke out nearly three years ago, Palestinian sources and hospital officials reported.Police said at least five Palestinians were killed but could not immediately confirm higher casualty figures reported by east Jerusalem hospitals, while Army Radio reported at least four Jews were wounded. Yossi Tuvias, the Border Police commander in Jerusalem, described the violence as "organized riots."

Palestinians massed at the Temple Mount after calls by Moslem religious leaders to "protect" Islam's third holiest site because they believed a fringe Jewish religious group would try to lay a cornerstone for the Third Jewish Temple, which would replace Islamic holy sites.

The Jewish group, called Temple Mount Faithful, had issued leaflets calling for a mass Jewish pilgrimage to the Temple Mount Monday on the Jewish festival of Succot. During the holiday, thousands of Jews converge on Jerusalem, its walled Old City and the Western Wall.

The Western Wall, Judaism's holiest site adjacent to the Temple Mount, was the outer retaining wall of the destroyed Jewish Temple.

Slogan-shouting by Palestinians on the Temple Mount, where the Dome of the Rock and Al Aqsa Mosque are located, sparked volleys of tear gas by Israeli security forces at midmorning, Palestinian sources said.

The violence spiralled with stone-throwing at the forces and thousands of Jewish worshippers below the Temple Mount at the Western Wall. Palestinians broke into the police station on the Temple Mount and burned it down.

The firing of rubber bullets, and apparently live ammunition, quickly followed, the sources and Army Radio reporters said. Shots were heard almost continuously for nearly an hour as the wounded were evacuated from the Old City.

Tuvias said police discovered large barrels filled with stones, nails, steel bars and bottles blocking the entrances to the Temple Mount and delaying the advance of police reinforcements sent to quell the violence.

Violence in the Arab neighborhoods of Jerusalem and surrounding villages has been on the rise in recent weeks. But the Old City clashes Monday were the worst violence in Jerusalem since the start of the 34-month-old Palestinian uprising.

"I think that in the last three years, this is a riot that we, at least, have not known the likes of," Tuvias said.

Religious Affairs Minister Avner Shaki was quoted by Army Radio as saying, "This is a very serious event that demands a response from the security forces that is not routine."