Israeli leaders Monday vowed to avenge the deaths of a Jewish woman and her three sons in the firebombing of a bus. The army said the Palestinian attackers were in custody, and there were reports two had confessed.

The attack in this West Bank town came 35 hours before Israel's parliamentary elections. It could drive undecided voters to the Likud bloc of Prime Minister Yitzhak Shamir, who has advocated a hard line in dealing with violence.In newspaper interviews published today, Shamir and his rival, Foreign Minister Shimon Peres, promised revenge for Sunday's attack.

Defense Minister Yitzhak Rabin asked the army's chief prosecutor to investigate whether the death penalty could be used against the assailants, calling them "murderers of women and children who have lost all shades of humanity," Israel radio reported.

The radio said the army rounded up dozens of Palestinians in Jericho. It said two suspects in custody admitted taking part in the attack.

In Jerusalem Monday, more than 1,000 mourners attended a funeral for the victim, 27-year-old Rachel Weiss, and her sons, Rafael, Netanel and Efraim, aged 9 months to 31/2 years. Many mourners wept and wore the traditional black clothes of Orthodox Jews. A banner stetched across the street said "Oh what has befallen us?"

Mrs. Weiss, her husband and her sons lived in Jerusalem and were returning home from northern Israel at the time of the attack on the bus. The husband escaped without serious injury, army officials said.

Five other bus passengers were injured in the attac, one a soldier who was seriously burned.

Two of those injured are immigrants from Pittsburgh: Dov Blum, 35, who suffered serious burns on his face, and his wife, Cindy, burned on her face and back, said Ruth Mekel of Hadassah Hospital in Jerusalem.

The attack claimed the largest number of Israeli lives in a single assault since the Palestinian revolt against Israel's 21-year occupation of the West Bank and Gaza Strip broke out almost 11 months ago.

A total of 305 Palestinians and 10 Israelis have been killed in the uprising, which began Dec. 8.

Maj. Gen. Amram Mitzna, the West Bank commander, told reporters in Jericho Monday that a curfew was imposed on the town of about 17,000 Arabs 18 miles east of Jerusalem.

The attackers tossed the firebombs from a banana plantation next to the road. As reporters watched, an army bulldozer plowed under rows of banana trees to prevent future ambushes.