In an emotionally electric climate of Arab firebomb attacks and reprisal air raids, Israelis Tuesday cast ballots in watershed elections expected to determine the future of the occupied lands.

More than 300 Arabs and 10 Jews have been killed in the occupied West Bank and Gaza Strip in the nearly 11-month-old Palestinian uprising against 21 years of Israeli rule.Election officials reported a heavy voter turnout under clear skies. A massive security force protected polling places. The army sealed off the occupied lands, where a Palestinian general strike was taking place.

Political observers said the slaying of four Israelis in a firebomb attack Sunday would tilt undecided voters to Prime Minister Yitzhak Shamir's right-wing Likud bloc, which opposes Israeli withdrawal from the occupied lands.

Labor, led by Foreign Minister Shimon Peres, has offered such a withdrawal in return for peace.

As its citizens voted, Israel raided Arab guerrilla targets in Lebanon in apparent retaliation for a firebomb attack Sunday. Lebanese police said four people were killed and 15 wounded.

In Arab east Jerusalem, assailants Tuesday threw a firebomb at a car, injuring three people, police said. Witnesses said the car was plastered with stickers for the Likud bloc and was being used to transport voters.

By midafternoon, 41 percent of the electorate, or about 1,090,000 voters, had cast ballots. Results were to be announced after polls closed at 10 p.m. (1 p.m. MST).

Neither Labor nor Likud has succeeded in gaining a majority in the 120-member Parliament since the Jewish state was established in 1948. Polls indicated they would fail again.

The situation has forced Labor and Likud to form alliances with minor parties that have gained influence beyond their numbers. Twenty-seven parties were entered in the election.

Likud and Labor formed a fractious coalition after the 1984 elections, when neither party could arrange a majority with the small parties.

Election officials said the turnout was heavy, indicating that 75 to 80 percent of eligible voters would cast ballots. In the 1984 election, voter turnout was 78.7 percent.

Analysts said the high turnout would favor Likud because much of its support comes from lower- and working-class voters more easily deterred from voting by bad weather and transportation problems.

Police reported 74 incidents ranging from fistfights to unlawful campaigning near polling stations. Three people were reported arrested.

The army sealed off the occupied territories for 48 hours, beginning at 11 p.m. Monday, and imposed curfews on refugee camps in Gaza. Journalists were barred without army permission and escort from entering the territories, where a Palestinian general strike was under way.

Bank employee Rahamim Fadikler voted in a working class Jerusalem neighborhood.

"My family and I vote for Likud," he said. "The people here don't want to return the territories. We suffered the shelling in 1967 and we don't want to see it again."

He was referring to shelling of settlements along the border before Israel captured the territories from Jordan and Egypt in the 1967 Middle East War.

Shamir favors the strengthening of Jewish settlement in the occupied lands, which 70,000 settlers share uneasily with 1.5 million Palestinians.

In the election, 2.9 million voters were eligible to cast ballots. Results were not expected until Wednesday.

More than 13,000 policemen and civil guardsmen were deployed at the 4,800 polling stations.