Up on the hill a few miles from here, the church bells rang yesterday, summoning the faithful in the Christian town of Marjayoun to Easter services.

Just a week ago in the same hills of southern Lebanon, some 70 men, women and children who had sought refuge in a mosque were slain by Christian militiamen in this largely Moslem town.

The tragedy, one of many that have befallen this blood-soaked country, followed Israel's invasion of southern Lebanon, which has disturbed the delicate 18-month-old balance between the warring Christian and Moslem communities in the region.

When the 1975-76 civil war ended, the fighting in the south did not stop. Israel has not allowed Syrian peacekeeping troops into the south and has given support to the Christian militiamen as they continued to battle their leftist Moslem foes.

Khiam had served as a base for Palestinian guerrillas and their leftwing Lebanese allies, but the Israelis drove them out the first day of the invasion. The Israeli forces went on in pursuit of the Palestinians leaving Khiam unprotected from the Christian militiamen who followed.

Israeli Chief of Staff Lt. Gen. Mordechai Gur had alluded to the killings in the mosque in elliptical language last week when he said his men were encountering difficulty in protecting Moslem villagers from acts of revenge and looting by Christian soldiers.

Quoted in the Jerusolem Post, Gur cited cases of looting "and much worse" and said that in the heat of the battle it was not always possible for Israeli troops to prevent such occurrences.

The Mosque slayings took place well after the brief battle for Khiam. Although Gur hinted at what took place, there has been a general reluctance to discuss the incident for fear of setting off further religious violence. News about Khiam was censored from all Lebanese newspapers.

The fate of the Moslem town came as no surprise to the Lebanese or to foreigners who lived in Lebanon during the civil war. It is just another link in a long list of similar happenings.

Karantina, Damour and Tal Zaatar are not household words in Israel, but they are the sites of some of Lebanon's most bitter acts of communal violence. The first and third were perpetrated by Christians against Palestinians; at Damour, Palestinians killed 500 Christians and dynamited most of the town's buildings.

Here in Khiam on a warm, sunny Easter yesterday the streets were empty of civilians. The usual signs of war abound - a minaret almost cut in burst water main, and cinder block facades riddled by holes, shell casings and overturned car carcasses whose permission was required.

Reporters found access to parts of Khiam difficult. Even Isreali Army public relations officers were unable to locate the local Israeli commander.

"Even if the chief of staff comes here without a pass I'll not let him through," a young Israeli soldier said on three occasions at the key crossroad leading to Khiam.

Seven hours later, two reporters were able to arrange a meeting with the Israeli commander in Marjayoun who had sent word that Khiam was off limits.

Asked point blank about the mosque slayings, the commander said: "Yes, it was an accident. Yes, about 70. They are all buried."

Did he worry about his Christian allies' behavior in this instance and in the future?

"We are soldiers," he said. "We cannot tell you what we think."

He did produce the precious pass, however.

In the past week, the Christian troops, undermanned despite 300 reinforcements sent from near Beirut, have had to be called to order by the Israelis.

When they shot over the heads of a first U.N. peacekeeping contingent, an embarrased Israeli spokesman felt obliged to underline that the Christians did not call the shots in southern Lebanon.

And when on Saturday Gur visited Maj. Saad Haddad, the Christian commander in the south, and swore he would appear to be that moderation is was just a suggestion that the Israeli general was passing along a plea for moderation.

But if there is any lesson to be learned from the expanding violence spawned by the Lebanese civil war it would appear to be that moderation is in precious short supply.

Whatever their faults the Palestinians by their presence here at least kept Christian and Moslems from massacring each other.

And whatever the sense of outraged at the Palestinian commando carnage two weeks ago on the Haifa-Tel Aviv road, statistically it killed less than half the number murdered in a Khiam Mosque.