Israeli troops shot dead four Arabs and wounded 150 in clashes in the occupied Gaza Strip Saturday, military and Palestinian sources said.

Palestinian sources said a fifth Arab, a woman, died of a heart attack after inhaling tear gas. Military sources confirmed a fifth death but said the circumstances were unclear.The clashes were the bloodiest between Israelis and Palestinians since 18 Arabs were killed by police on Jerusalem's Temple Mount in October.

The incident began when soldiers encountered a group of masked activists carrying knives in Rafah at the southern tip of the Strip on the border with Egypt, military sources said.

The group refused an order to halt, and the soldiers opened fire, killing two people, they said.

Thousands of enraged Rafah residents clashed with soldiers after the killings and two more Arabs were killed.

Witnesses in Rafah said an army helicopter dropped stones and tear gas, gravel-shooters sprayed egg-sized stones, and soldiers fired live ammunition, metal ball bearings, tear gas and percussion grenades at thousands of demonstrators who threw stones and fire bombs.

Staffers at Nasr Hospital said at least 150 wounded Palestinians from Rafah, Khan Younis and adjacent refugee camps were brought to the hospital.

Military sources said 91 people had been wounded and all but 18 had been released by Saturday night.