Lebanese Army troops opened fire on an Israeli patrol that had ventured across newly drawn front lines in southern Lebanon today.

The Lebanese Army command said that the Israeli patrol advanced to the village of Kawthariyet Siyad, located northeast of Tyre and about two miles west of Israel's latest defense line as it runs north from the Litani River to the western part of the Bekaa Valley.

Lebanese Army troops opened fire, forcing the Israeli patrol to halt, the Lebanese command said. The Israelis then moved up a motorized patrol supported by tanks, and the two sides exchanged fire until the Israelis withdrew after an hour and a half, according to the Lebanese command. The Lebanese statement listed no Army casualties but said one civilian was wounded.

Israeli military officials said the incident took place within the Israeli-controlled area, Washington Post correspondent Edward Walsh reported from Jerusalem. According to the Israeli account, an Israeli foot patrol east of Kawthariyet Siyad fired at "two terrorists armed with an AK47 rifle and rocket-propelled grenades who were advancing toward our forces."

When a Lebanese Army unit responded by firing at the patrol from the village, the Israeli officials said, the patrol "took cover and waited for the Lebanese to cease fire. Since the Lebanese continued to fire," the patrol fired "several bursts" and later "a single tank round was fired as a warning, . . . aimed wide so as not to hit the Lebanese," Israeli officials said.

Local journalists who went to the village said two Israeli armored personnel carriers were damaged in the incident. The local journalists, whose reports could not be confirmed, also said an Israeli helicopter landed near the village shortly after the battle and dropped smoke bombs to evacuate Israeli wounded.

One of the reporters who visited the area said that when the shelling began, elements of the Shiite Moslem National Resistance Movement rushed to the scene and joined Army soldiers in firing at the Israelis. He said one Lebanese Army soldier and one resistance fighter were slightly wounded. Again, there was no official confirmation.

This month's pullback by Israeli troops to the Litani, though largely credited to guerrilla operations against Israeli soldiers and their local allies, has heartened the Lebanese Army command and buoyed its confidence in extending its much challenged authority.

Officials of the mainstream Shiite Amal organization who traveled to the scene of today's fighting praised the Lebanese Army and encouraged it to persist in standing up to Israeli forces. Today was the third time Israeli troops had penetrated Lebanese-held territory north of the Litani River since their pullback from the Sidon area, but it was the first time they encountered resistance from the largely Shiite 12th Brigade of the Lebanese Army.

Last Thursday an Israeli force entered the village of Zrariye, just north of the Litani. Yesterday an Israeli foot patrol searched orange groves and orchards on the coastal road north of the river for about half an hour.

Yesterday, Israeli troops imposed a dusk-to-dawn curfew and tight restrictions on traffic in regions south of the Litani in an effort to crack down on resistance activity. Israeli helicopters dropped leaflets in the Tyre area warning residents to observe the curfew. The leaflets cautioned that suspicious-looking cars parked at roadsides would be blown up and ordered motorists never to drive unaccompanied.

The ban on unaccompanied drivers was seen as an attempt to reduce opportunities for suicide bombers. A suicide bomber injured at least 10 Israeli soldiers east of Tyre earlier this month.

Shiite activists have stepped up attacks against Israeli soldiers in the belief that this would accelerate their withdrawal from Lebanon. Israeli military authorities have retaliated with force, sending troops into villages and bulldozing and destroying houses. Several hundred families have fled the Shiite heartland from villages that were entered by Israeli troops last week.

The central command of Amal, led by Nabih Berri, minister of justice and state minister for southern Lebanon, vowed tonight to escalate resistance against all Israeli positions everywhere. Previously, the National Resistance Movement and Amal had specified that resistance activity would be confined to Lebanese territory. Today, Amal official Daoud Daoud said in a television interview, "We can take the national resistance to Israeli settlements and destroy houses and inhabitants inside Israeli territory."