Israeli Prime Minister Shimon Peres expressed his "deep sorrow" today at "the tragic death" of two CBS News employes killed by Israeli tank fire in southern Lebanon yesterday, but said they were fired on because they were "in the midst" of a group of hostile guerrillas.

Edward M. Joyce, president of CBS News, rejected Peres' version of the incident. In a cable to Peres from New York, Joyce said the network was "disappointed that you chose to ignore the testimony of eyewitness journalists on the scene who made it clear that the group fired upon was not armed or engaged in hostilities, that the cameras as well as the press markings on the cars were in clear view of the tank crew and that the Israeli attack was entirely unprovoked."

Peres' message to Joycemaintained that the tank crew that fired at the men "did not deviate from the strict orders concerning the protection of innocent bystanders."

Peres added: "I reiterate Israel's longstanding and unqualified commitment to freedom of the press and totally reject any suggestion that the incident was anything but a derivative of the tragic situation in Lebanon and the circumstances under which we are forced to carry out our duty to protect the lives of our soldiers."

The two Lebanese employes of CBS, Toufiq Ghazawi, a cameraman, and Bashir Metni, a sound technician, were reportedly in an automobile when it was hit by tank fire near the village of Kfar Melki. The driver of the car was injured in the incident.

Journalists who were in the same area were quoted as saying that the group of newsmen was clearly identifiable as such and that the Israeli tank, stationed about 500 yards away, appeared to fire at them deliberately. Last night, the Israeli military command said the tank fired on "armed men who were taking firing positions," and that from the distance involved "it appeared that the CBS crewmen were among the armed men in the village."

One of the eyewitnesses who contradicted the Israelis' account, French television reporter Marine Jacquemin, told The Associated Press, "The cameraman, with his camera on his shoulder, was taking a last shot. Then came the shell. The cameraman flew up into the air, the sound man was hit in the breast. The driver, he fell injured."

She and a colleague, Alain Menarques of France Interne radio station, said there were no militiamen in the area.

There have been no reports that armed guerrillas were killed or injured as a result of the tank fire.

A military spokesman in Tel Aviv said today that a preliminary investigation had determined that the tank crew "acted in accordance with regulations" and that there would be "no special inquiry" into the incident as demanded by CBS. Israel radio said Peres had accepted the Army's version of the incident and ruled out any investigation other than the Army's routine review of the action.

The CBS News president's reply to Peres renewed the network's call for "a complete, vigorous and independent investigation of yesterday's tragedy." Joyce said he was sending Ernest Leiser, a CBS News vice president, to Jerusalem to discuss the incident with Israeli officials.

In raids on four southern Lebanese villages yesterday, Israeli soldiers killed 21 people they described as Shiite Moslem guerrillas and wounded seven others, in addition to the two CBS newsmen who were killed. The newsmen were believed to be the first killed by Israeli fire in the Lebanese conflict.

Peres' quick message to Joyce, and the decision to make it public, underscored Israeli sensitivity to the increasingly adverse publicity on what has been dubbed even in the Israeli press as Israel's "iron fist" policy in southern Lebanon.

Faced with a mounting wave of attacks by Shiite Moslem guerrillas that has resulted in numerous Israeli casualties, the Israeli Army has retaliated with a series of raids on suspected village strongholds of the guerrillas. More than 100 men identified by the Israelis as guerrillas have been killed or wounded recently in these raids, while dozens of houses have been destroyed and large amounts of weapons and explosives have been confiscated.

The stepped-up tempo of guerrilla attacks and Israeli village raids has attracted renewed interest in southern Lebanon at the same time that the Israeli Army has lost much of its ability to control access to the territory it still occupies.

This has been particularly true since Feb. 16, when the Israelis abandoned the permanent defense line they had built along the Awwali River in the first stage of their planned three-staged withdrawal. The new Israeli line has no fixed positions and few clear-cut crossing points, making it difficult to prevent journalists based in Beirut from traveling south into the Israeli-controlled zone. Many of the Israeli raids, such as those yesterday, have been in areas the Israeli Army evacuated last month.

Last month, in a renewed attempt to restrict access to southern Lebanon, the Israeli military command announced a ban on journalists entering Israeli-occupied territory from the north and said that Army checkpoint commanders had been issued "strict orders" to enforce the ban.

However, the order appears to have been largely ineffective and, as yesterday's incident demonstrated, it does not prevent journalists from being nearby when the Israelis reenter areas from which they withdrew last month.

Journalists who encounter Israeli soldiers in southern Lebanon are seldom stopped once it is clear to the soldiers that the journalists pose no threat to them. The soldiers in the field, aware that they will soon be out of Lebanon and concerned above all with their own safety in the hostile environment, clearly have little interest in enforcing the ban against journalists that was issued by the military command in Tel Aviv.

The Israelis do control access to southern Lebanon by journalists based in Israel, who must cross the Israeli-Lebanese border to reach the territory. Early last year, in a reversal of policy, the Army announced that journalists would not be allowed across the border unless accompanied by armed escort officers from the Israeli Army spokesman's office. In the months since then, however, numerous exceptions to this rule have been granted.

The Army here has allowed no coverage of its raids on Shiite villages by Israel-based journalists. Most information about the raids and their aftermath has come from United Nations officials in the area and journalists from Beirut and Sidon who reach the villages, usually after the Israelis have left.