ISRAELIS RAISE STAKES IN LEBANESE ATTACKS : GUNBOATS BLOCKADE BEIRUT; HEZBOLLAH EASES UP ON ROCKET LAUNCHES.

Byline: Serge SchmemannThe New York Times

Israeli gunboats blockaded Beirut and other Lebanese ports Saturday, and Israeli guns rained shells on southern Lebanon as Israel steadily raised the heat of its operation against Islamic guerrillas.

Israeli commanders noted that the guerrillas of the Party of God, the Iran-backed organization also known as Hezbollah, fired only a few random Katyusha rockets into northern Israel on Saturday, suggesting that they had lost the fixed positions from which to fire the large salvos of earlier days.

``They've been able only to fire a very small number of Katyushas, about four since last evening,'' an Israeli officer told reporters in northern Israel on Saturday. Nonetheless, Israel's northernmost city, Qiryat Shemona, was virtually deserted, as residents fled to the south for safety.

By contrast, the Israeli army - now in the third day of its offensive to strike at the Party of God and to force Syria and Lebanon to curb the guerrillas - said it had fired thousands of artillery rounds at villages in southern Lebanon where the Israelis said guerrillas had bases.

The Israelis said that more than 200,000 villagers had fled ahead of the strikes, clogging roads and creating a major refugee problem for the Lebanese government and for Syria, which maintains 35,000 soldiers in Lebanon. Lebanese reports put the death toll at 24, including one Israeli soldier.

In the deadliest incident of the day, an Israeli helicopter fired a rocket at a Lebanese ambulance. According to a Reuters photographer who witnessed the attack, two women and four girls were killed and several people wounded in the ambulance, which was hit after driving through a United Nations checkpoint.

An Israeli army spokesman said the ambulance had been attacked because it was carrying a Party of God guerrilla from one position to another.

``If other individuals in the vehicle were hit during the attack, they had been used by the Hezbollah as a cover for Hezbollah activities,'' the spokesman said, adding that Israel had warned Lebanese citizens to keep clear of guerrillas.

The Israeli blockade of Beirut was the first since 1982, although Israel has blocked other ports more recently. Thursday and Friday, Israeli helicopters struck targets inside Beirut, also for the first time since the 1982 invasion of Lebanon.

The Lebanese army issued a statement saying, ``Israeli gunboats are intercepting commercial ships heading to and from Beirut port within Lebanese territorial waters.'' There were reports that the Israelis ordered commercial vessels to stay 12 miles from shore, and that the ports of Sidon and Tyre were also closed.

Israeli officials said their country's navy was checking ships for weapons bound for the Party of God guerrillas. The blockade also served to increase the pressures on the Lebanese and Syrian governments.

The Lebanese government, powerless to block Israel, lodged a formal protest with the U.N. Security Council and asked for an emergency meeting of the 22-nation Arab League. Lebanese officials, including Prime Minister Rafik Hariri, also met in Damascus with Syrian President Hafez Assad.

But Israeli officers spoke of continued operations inside Lebanon for several more days. In the last such strike, in 1993, the Israelis maintained their attack for seven days before agreeing to a U.S.-brokered cease-fire.

Friday, an Israeli strike against a Syrian anti-aircraft position, in which a Syrian soldier was killed, raised fears that Syria would be drawn into the fray. But there was no indication Saturday of any Syrian action, and Western diplomats in Israel said Assad had long been careful not to provoke any armed confrontation with Israel.

The Party of God and other Islamic militant groups joined in threatening new violence against Israel.

Sheik Hassan Nasrallah, the head of the Party of God, called on suicide bombers to enter the fight. ``Due to the developments, we call on the martyrs' brigade to join their predetermined posts, and we call for general mobilization in the ranks of Hezbollah,'' he said over the movement's television outlet.

Last month, a Party of God suicide attacker blew himself up near an Israeli patrol in southern Lebanon, killing an Israeli soldier and wounding five.

The two Palestinian resistance movements, Hamas and Islamic Jihad, also vowed to avenge the Israeli attack. A joint statement issued to a news agency in Beirut said, ``Our heroic suicide attackers will strike deep in the Zionist territory.''

Bombers acting in the name of Hamas and Islamic Jihad struck four times in late February and early March, killing more than 60 people. Their attacks led Israel to clamp severe restrictions on Palestinian areas and to suspend peace talks with Syria.

Israel opened its operation in Lebanon on Thursday, charging that two Party of God rocket attacks on northern Israel this month were the last straw in a steady escalation of guerrilla operations over the last year.

The Party of God was formed in 1982 to fight the Israeli invasion of Lebanon, and its stated goal remains to oust the Israelis from the nine-mile-wide buffer zone they maintain in southern Lebanon.

In the summer of 1993, Israel staged a similar operation inside Lebanon, which lasted for seven days and took 130 lives. It ended with an unwritten agreement between Israel and the guerrillas not to strike at civilian targets.

But Israel charged that the guerrillas had used the pact to set up fixed positions in villages, and that it used any excuse to fire Katyusha rockets into northern Israel. The two attacks in early April followed incidents that Israel termed accidental.

CAPTION(S):

2 Photo

Photo: (1) Israeli Prime Minister Shimon Peres visits res idents in a bomb shelter in Qiryat Shemona, the nation's northernmost city.

(2) Shiite Muslims flee their village of Mansouri, Lebanon, as the Israeli military's bombardment of Hezbollah guerrillas continued Saturday.

Associated Press