Sheik Hasham Hussendair, the Gaza Strip's ranking Moslem leader and an outspoken supporter of the Egyptian-Israeli peace treaty, was stabbed to death in front of his home last night, occupation authorities said today.

The Popular Front for the Liberation of Palestine, in a message clearly intended to discourage support for autonomy in the occupied Gaza Strip and the West Bank of the Jordan River claimed responsibility for the assassination.

Hussendair, 72, was slain as he returned home at 8:30 p.m. from prayers at the local mosque. Officials said he was stabbed in the heart by a lone assailant. Until just two weeks ago, the Israeli Army provided bodyguards for the sheik but, at his own request, they were withdrawn.

Hussendair, a Moslem priest, visited Egypt twice in the last six months to show his support for the peace treaty and the proposed limited self-rule plan for the territories occupied by Israel in the 1967 six-day war.

Recently, he tried to organize a pilgrimage of 150 Gaza residents to Cairo to demonstrate support for Egyptian President Anwar Sadat.

However, the trip was canceled when he was able to enlist only 50 residents.

Militay sources said tongith that five months ago a lone gunman burst into Hussendair's garden and pointed a pistol at the sheik. However, one of Hussendair's sons shouted a warning, and the gunman fled before firing.

Since then, according to military sources, Hussendair had been regarded as a prime target for an assassination by Palestinian terrorists, who reportedly are determined to divert attention from Egyptian-Israeli detente and focus Gaza loyalty toward Jordan.

In Beirut, a Palestine Liberation Organization spokesman said, "Our people in the occupied territories executed this traitor" and added that the person who stabbed Hussendair had "risen from the masses," the Associated Press reported.

The PLO said the "execution" should be an example to all those who collaborate with Egypt and Israel.

Sources said that after the first assassination attempt, the Israeli military governor in Gaza posted a 24-hour guard on Hussendair's house but that after three months of the protection the sheik asked that it be withdrawn.

"He felt it called attention to himself as a collaborator," a military source said.

Officials said that after returning from his last trip to Egypt 2 1/2 weeks ago, Hussendair received numerous letters threatening his life.

After the return by Israel last month of the Egyptian town of El Arish, Hussendair repeatedly advocated open borders between the town and Israel and proposed that workers from El Arish be allowed to work in Israel.

More than 2,000 Gaza residents attended Hussendair's funeral today, a surprising turnout in light of the menacing message attached to his death by the Popular Front. Two Israeli Army colonels from the Gaza Strip military governor's office attended. Not attending, however, was Mayor Rashad Shawwa, who has been critical of the peace treaty and the autonomy plan.

Hussendair's son, Mamum, who recently was paroled from a 15-year prison sentence for membership in the Fatah terrorist organization, declared at his father's funeral that "mercenaries" were responsible.

Moderate Palestinian sources tonight said that the Popular Front apparently acted because it has been evident that a sizable majority of Gaza residents support the principle of autonomy, providing that it could lead to an independent state. The Gaza Strip, with its close ties to Egypt, has been regarded as a possible testing ground for self-rule independent of the West Bank, assuming that West Bank opposition to the peace plan remains adamant.