Nearly 48 hours after a terrorist group announced that it had killed U.S. diplomat William Buckley, authorities had found no proof that the "execution" has been carried out.

Senior U.S. Embassy officials said today that they had "no word so far" that Buckley's body had been found. The mysterious Islamic Jihad announced Buckley's imminent "execution" early yesterday after publication of a communique in which the terrorists claimed the killing was in retaliation for Israel's raid on Palestine Liberation Organization Chairman Yasser Arafat's headquarters in Tunis Tuesday.

"We have received nothing to authenticate this claim, and no corpse has been found," Gen. Osman Osman, Lebanon's police commander, said today.

The fact that Islamic Jihad has not produced Buckley's body has raised speculation here and in Washington that Buckley may have been killed long before Friday's communique. However, sources in Washington said there was no way to confirm this, and photography experts in Beirut said yesterday that the Polaroid snapshot of Buckley delivered with the terrorists' communique was a fresh one.

There also was no sign today of three missing Soviet Embassy officials kidnaped by another Moslem fundamentalist group Monday.

The Soviet Embassy, down to a skeleton crew after the evacuation of up to 100 staff members and dependents early yesterday, asked that Lebanese authorities step up their search for the missing officials. Lebanese militia searched suspected terrorist hideouts in west Beirut, diplomatic sources told reporters, but found no sign of the kidnapers or their victims.

The group claiming to hold the Soviets, the Islamic Liberation Organization, demanded that Syrian-backed forces lift their siege of Tripoli, where Sunni Moslem fundamentalists are dug in. The body of Arkady Katkov, 32, a consular secretary of the Soviet Embassy, and one of four Soviets kidnaped, was found Wednesday.

Fighting in the Tripoli area has eased since a cease-fire went into effect yesterday. Asem Kansul, secretary general of the pro-Syrian Baath Party, told news agencies that "the cease-fire in Tripoli represents a glimmer of hope for the Soviets."

A spokesman for Tawheed, the fundamentalist group in Tripoli, said Syrian peace-keeping troops would be allowed to enter the city Sunday and collect heavy weapons from both of the warring sides.

In Washington, State Department and White House spokesmen said the United States assumes Buckley is still alive but has no new information about him.

Buckley, abducted from his car in west Beirut on March 16, 1984, is one of six Americans believed held by the Islamic Jihad, which is demanding that Kuwait free 17 prisoners convicted of terrorist bombings in 1983.

The timing of the Islamic Jihad's communique, so soon after the slaying of the Soviet official by another fundamentalist group, raised questions about the terrorists' intentions. Despite professing to act in retaliation for U.S. involvement in the Israeli raid, Islamic Jihad, in the statement, expressed strong sentiments against Arafat, believed to have been the target of the Israeli raid, describing him as "defeated." It said Jordan's King Hussein and Egyptian President Hosni Mubarak were "groveling at the doors of America and France."