The Israeli Army moved forcibly today to evict its erstwhile Lebanese Christian allies from a military barracks in southern Lebanon, encountering resistance from militiamen and protest demonstrations by villagers in the area.

Israeli troops encircled the main southern Lebanon base of the Lebanese Forces militia near the port city of Sidon before dawn after the militia had failed to heed an Israeli order last week to move out.

It was the first serious clash between Israeli troops and the Phalangist militia, which it has helped arm, clothe and train over the years, since Israel announced last month that it would redeploy its troops into southern Lebanon.

The move appeared to be a strong message not only to the Lebanese Forces but also to other armed groups active in the area that Israel intends to be tough in exerting control over the array of unruly forces in southern Lebanon, no matter who they are.

Passively resisting, many of the 30 Christian militiamen refused to leave the barracks after being surrounded by 300 soldiers, according to an Israeli spokesman here. Some apparently had to be dragged out. A few militiamen and sympathetic civilians were still inside the barracks this evening, the spokesman said.

Thousands of villagers from the green hills above Sidon took to the streets in protest. They burned tires, rang church bells and chanted, "Don't make us turn into enemies," to the Israeli soldiers.

Israeli radio quoted chief of staff Lt. Gen. Moshe Levy as telling the foreign affairs and defense committee of the Knesset, Israel's parliament, that the action was taken because the Lebanese Forces had engaged in "unsuitable and uncoordinated activities," Washington Post correspondent Edward Walsh reported from Jerusalem. The radio said these included setting up unauthorized roadblocks and "harassing" Moslems and Palestinians in the area.

Israeli Defense Minister Moshe Arens said in a television interview in the United States last week: "It is not healthy to have independent militias running around causing troubles. Such militias tend to antagonize certain sections of the population."

There are a number of underground militias in southern Lebanon that are hostile to the Israelis and frequently attack their troops.Several other militias, that got their arms from Israel, roam the countryside. After the Israeli invasion in June 1982, Israeli forces embarked on an effort to create friendly militias and passed out guns liberally, in at least two instances even giving them to cooperative Palestinians. The policy added more fuel to the turmoil of southern Lebanon, and in some instances rival Israeli-armed militias engaged in shootouts.

But Israel's close relationship with the Christian Phalangist Party and its Lebanese Forces--once led by Bashir Gemayel, the Lebanese president-elect assassinated last year and brother of the current president--has turned out since the invasion to be increasingly embarrassing to the Israelis.

The Phalangist militia's massacre of hundreds of Palestinians in the Sabra and Shatila refugee camps in Beirut last September, following Bashir Gemayel's assassination, prompted a fierce reaction against the Israeli government of Menachem Begin.

Earlier this year, when the Phalangists in southern Lebanon were involved in a brutal campaign to drive Palestinians from their homes in the suburbs of Sidon, international relief agencies placed responsibility on Israel because its occupying forces were in control of the area.

Beirut radio said today that there were fistfights and incidents of face-slapping after 300 Israeli soldiers surrounded the Kfar Falous barracks of the Lebanese Forces east of Sidon.

Thousands of villagers turned out in protest, and three women were injured as Israeli troops used rifle butts against demonstrators, according to radio reports here. The Israeli spokesman here said one Israeli soldier had fired a couple of shots in the air to disperse crowds. A reporter in the area said that an Israeli soldier fired one shot between the legs of a Christian militiaman who argued with him.

Walsh reported from Jerusalem tonight that the Israeli Army announced that Syrian forces had directed small-arms fire at an Israeli position in eastern Lebanon, wounding one Israeli soldier. The announcement said Israeli forces returned tank and artillery fire.

The day of continued turmoil in Lebanon came as President Reagan's new Middle East envoy, Robert C. McFarlane, met with Lebanese President Amin Gemayel to discuss ways of securing the withdrawal of Israeli, Palestinian and Syrian forces from Lebanon. McFarlane later flew to Israel for talks with officials there.