Three Palestinian youths were shot dead in clashes with Israeli security forces and civilian settlers in the occupied West Bank and Gaza today, bringing to six the number of Arabs killed in the past nine days, and an Israeli border policeman was stabbed and seriously wounded.

As the violence in the occupied territories continued, Prime Minister Menachem Begin wrangled for the second consecutive day with Israel's deadlocked parliament, this time over the budget, and the prime minister said new elections were inevitable. No date for a vote was set, but aides to Begin said he would meet with his Cabinet and coalition leaders.

Speaking to reporters in Israel's parliament, the Knesset, Begin, who yesterday had threatened to resign after his government narrowly escaped being dumped in a no-confidence vote, said his Likud coalition cannot continue to govern indefinitely under the current 60-60 deadlock in the 120-member house, particularly with votes on key legislation coming up.

In a separate development, the Israeli Army command said an Army patrol intercepted and captured a three-man Palestinian guerrilla squad about three miles inside the Lebanese border today as the guerrillas apparently were headed toward an Israeli kibbutz.

An Army spokesman said the guerrillas were spotted inside Lebanon near the Israeli border kibbutz Hanita, about seven miles east of the Mediterranean coast. Israeli authorities said they carried rifles, ammunition and food and appeared to be planning an attack inside Israel.

Palestinian commando raids into Israel have triggered swift Israeli retaliation in the past, and last week Defense Minister Ariel Sharon warned that Israel "might be forced to take action" following what he said were 15 acts of sabotage in Israel and five guerrilla attacks in southern Lebanon in the previous two weeks.

The Palestinian deaths came as disturbances continued throughout the West Bank for the sixth consecutive day, and militantly nationalist mayors announced that a general strike in the occupied territory will continue through a scheduled U.N. Security Council debate on the current wave of unrest and the Israeli Army's response to it.

An 18-year-old Arab youth was shot and killed in the village of Bani Naim, about three miles east of Hebron, when a Jewish settler from the nearby Kiryat Arba settlement opened fire with an automatic weapon after being hit in the head with a rock thrown by protesting students, a spokesman for the Army command said. Three Kiryat Arba residents were injured in the clash, the Army said.

A 21-year-old Palestinian was shot and killed in the marketplace of the town of Jenin, on the northern edge of the West Bank, when he pulled a knife and stabbed an Israeli border policeman who attempted to question him, Israeli authorities said.

Officials said a border police foot patrol spotted the youth encouraging merchants to close their shops in protest, and that when the officers attempted to question him, he stabbed a policeman three times in the chest. As he ran away, he was shot by one of the officers, the authorities said. The policeman was reported to be in serious condition in a hospital in Afula.

Another Palestinian student was shot and killed in a demonstration in the village of Abasan, near Khan Yunis, when Army troops attempted to disperse a demonstration, the Army command spokesman said.

The Army spokesman said six Palestinian youths were wounded in the gunfire after troops first tried to disperse the crowd with tear gas, and then fired warning shots in the air.

Rock-throwing demonstrations were reported in Ramallah, where an Army officer was injured by a stone thrown at his car, and in Nablus, Bethlehem and Jericho.

On March 16, an Arab student was shot and killed in a clash with civilian settlers near the Shiloh settlement, but his body was not discovered until Friday. Also on Saturday, a 17-year-old Arab youth was shot dead by soldiers in a demonstration in El Bireh to protest the dissolution of the City Council by the military government, and on Monday another youth was killed by Army gunfire in a demonstration in Deir Ammar, near Ramallah.

The unrest in the West Bank and now Gaza has contributed to the political uncertainty in Israel and was a factor in yesterday's confidence vote. Begin did not say when he would move for a new election, but he said he was confident he could strengthen his coalition as a result. A close aide to the prime minister later said the question would be discussed with the Cabinet ministers and coalition leaders in the parliament, but that presumably no action would be taken until after the scheduled April 25 withdrawal of Israeli settlers from the last third of the Sinai Peninsula.

The aide also said the Cabinet will have to discuss the question of whether to force a new election by resigning, or by introducing a motion to dissolve the Knesset and schedule another parliamentary election. Begin was reelected to a second five-year term June 30 after asking the Knesset to advance the election five months following a coalition crisis stemming from the economic situation in Israel.

Begin said he wanted to resign after last night's confidence vote, but was overruled by the Cabinet. He noted that he could have resigned anyway, but said that would have alienated his ministers, who are not anxious for a new election.

If Begin moves to advance the election shortly after the Sinai withdrawal--which would be four years before his term expires--the vote could not be held for at least three months, according to Israeli law, and most probably balloting would not take place until November, when municipal elections throughout Israel are scheduled.

Begin's somber assessment of the future of his fragile Likud coalition came as the Knesset, in a tumultuous vote repeatedly interrupted by arguing on the floor, attempted to adopt a supplementary budget allocation proposed by the Likud.

In the morning, when a head count of members indicated that Likud absences would result in a defeat of the budget bill, the government requested a postponement. But later, when it was evident that Rabbi Haim Druckman of the National Religious Party was absenting himself from the chamber, and the government would be assured of a one-vote majority, the Likud called for an immediate vote.

Druckman, an opponent of the Sinai withdrawal, joined the opposition in last night's no-confidence vote and was the swing vote that caused the 58-to-58 deadlock. While a no-confidence motion fails in case of a tie, a deadlock would have defeated the budget measure.

The opposition alignment boycotted the vote, except for two members of the centrist party Shinui, and the budget supplement was adopted in the first reading, 58 to 2. However, when the measure came to a second reading in the afternoon, Druckman was sitting in his seat, apparently prepared to vote against the government, and the Likud announced a postponement of the vote until Monday to avoid certain defeat.

Earlier in the day, Likud strategists had said that if the coalition could survive two more weeks, until the Passover recess and the end of the Knesset's winter term, it would soon have behind it the April 25 Sinai withdrawal and, thus, the motivation for last night's defections by Druckman and the three-member nationalist Tehiya (Renaissance) party, which also is opposing the Sinai pullback.

An adviser to the prime minister said he expected that after April 25, Druckman would rejoin the coalition, and that Tehiya would either join Likud or tacitly support it. Moreover, he said, he expected that the two-member Telem faction, which was founded by the late Moshe Dayan, also would support the government, or even seek to join it, thereby broadening Begin's coalition to a comfortable majority.

"The prime minister's problems are all coming from the right. Labor and the left are never a problem because they don't have a chance for a majority. The problem is the people opposed to the Sinai withdrawal, and when the Sinai problem goes, our problem is over," the Begin adviser said.

After the withdrawal, the aide said, Begin would be in a position to entice the rightist opponents by offering to "consolidate Israel's control of the West Bank and Gaza Strip," either by promising to build more settlements or adopting resolutions that reaffirm Israel's intent to maintain perpetual control over the occupied territories.

"That's something that everybody's for," the Begin adviser said.

With Druckman remaining firmly in the opposition, however, Begin appears to have concluded that advancing the elections is the only certain way of broadening his majority and avoiding embarrassing defeats on other pending legislation.

Avraham Shapira, of the coalition's Agudat Yisrael party, today told Israeli radio that if Druckman stays in the opposition and the budget legislation fails, his party will defect from the coalition and bring down the government on the issue of proposed amendments to the "law of return" for new immigrants to Israel. Agudat Yisrael is demanding that the law be amended to require that new immigrants who converted to Judaism be converted by Orthodox religious law, and not by Reform rabbis.

Shapira said that if the Likud should fall on a religious question, it would give the government a "better image" than if it were to fall on a political question.