In the first fatality since Shiite Muslim guerrillas took over southern Lebanon on Wednesday after Israel's withdrawal, a guerrilla shot and killed a 50-year-old Christian man and wounded another Christian in Rmaish village, a former stronghold of the now-defunct Israeli-backed South Lebanon Army militia.

Police, in a terse statement, said the suspect was apprehended, describing the shooting as an "individual incident." Hezbollah, the leading guerrilla group in south Lebanon, denied involvement.

There have been scattered reports of break-ins and looting in Christian towns in the predominantly Shiite region, but until Sunday none of the revenge attacks that had been feared. The government sent a few hundred policemen to the region to try to ease Christian anxiety.

Also Sunday, two girls were killed and their father injured when their vehicle drove over a land mine on a side road in the south, police said. Another man was hurt when a mine exploded as his bulldozer was clearing a road of rubble. Police had further details.

Sunday's violence showed how tenuous the security situation remains in southern Lebanon in the absence of government troops and U.N. peacekeepers, who are yet to deploy in the areas evacuated by Israel and its Christian-led militia. The militia's 2,500 mostly Muslim members have surrendered to authorities or fled to Israel.

The Israel army said hundreds of Lebanese gathered Sunday at the Fatima crossing about 50 miles southeast of Beirut, and that troops fired a stun grenade and used live ammunition when some tried to cross into Israel.

A 15-year-old boy was seen hit in the back but continued to walk, an indication his injury was not serious. Two other people reportedly suffered injuries, but the army confirmed only one more. It said troops fired warning shots and a man was injured by a fragment of a concrete pillar that was hit by a bullet.

Since Israel withdrew its forces from southern Lebanon last Wednesday after an 18-year occupation, Lebanese have been demonstrating in support of the Hezbollah, throwing stones and sometimes firebombs toward Israeli troops. Several armed guerrillas came to the border Sunday and urged people not to throw stones.

Israeli Prime Minister Ehud Barak told a Cabinet meeting that conditions along the border were "delicate and fragile," but that every day that passes quietly helps to ensure stability.

"The army has clear instructions to open fire only for incidents of rescue or self-defense," Barak said, according to a statement. "The army won't open fire for any other reasons."

Barak's office also denied media reports that Hezbollah and the Israeli army had reached a temporary cease-fire agreement.

President Clinton, in a telephone conversation with Barak, congratulated him on the withdrawal and expressed the hope that calm and stability would prevail on the border, Barak's office said.

The U.S. ambassador to Israel, Martin Indyk, called on Lebanon to send its army into the border area, as stipulated in the U.N. resolution that called for Israel's withdrawal, and to seize control from the guerrillas.

The Israeli army, meanwhile, denied Lebanese reports that the air force violated Lebanese air space Sunday, insisting that the training exercises in question took place over the Mediterranean, outside Lebanese areas.

On Saturday, the army completed an evacuation of two outposts in the Chebaa farms region, north of Israel's border.

Lebanon has called for a complete evacuation of the area and Hezbollah has warned it will continue attacks unless troops leave the farms. But Barak said Sunday that more than 90 percent of the Chebaa farms will not be evacuated because they are not in Lebanese territory according to U.N. maps.