WASHINGTON--President Reagan denied yesterday the United States had tried to kill Moammar Khadafy during the bombing of Libya, but a new wave of terrorism linked to the attack claimed an American life.

Hospital officials in Lebanon reported yesterday an American taken hostage in Beirut was among three Westerners executed to avenge the American strike against Libya.

Officials of Great Britain said they had "firm evidence" of Libyan involvement in the kidnapping of the other two victims whose bodies were discovered along with that of the American, identified as Peter Kilburn. Reagan administration officials said they wanted to examine that evidence before contemplating any further counterterrorist moves.

As for Khadafy, Reagan said as he left the White House: "We weren't out to kill anybody."

The president was responding to reporters' shouted questions about whether the administration hoped to kill the Libyan leader. The Washington Post quoted unidentified sources yesterday as saying the raids were planned with that goal in mind.

Secretary of State George Shultz and the Pentagon's number two official, Deputy Defense Secretary William H. Taft, did acknowledge the United States had hoped the strike might foster an internal revolt against Khadafy. Taft also said the United States was "certainly prepared" to deal with the consequences of killing khadafy during the raid, but stressed the administration did not set out to do so.

Defense Secretary Caspar W. Weinberger said Reagan had ordered the strike reluctantly and as "a last resort" because European allies would not join in an economic boycott. He said Reagan probably would urge a boycott once again before ordering military action if additional terrorists acts are tied to Khadafy.

As the various administration officials spoke, protests against the U.S. strike escalated; Americans were evacuated from the Sudan; and bomb threats inundated police authorities here.

White House spokesman Larry Speakes, in New York with Reagan, said the president "wanted all the families of the hostages to know everything we do."

He said that officials "have been in touch with all the families of American hostages and provided them with all the information we have."

The bodies of three Westerners were found Thursday near Beirut. A note with the bodies said the three had been slain in retaliation for English Prime Minister Margaret Thatcher's decision to allow the U.S. bombers that attacked Libya to fly from British bases.

Two of the men were identified earlier as missing British hostages, Leigh Douglas and Philip Padfield.

In London, Foreign Secretary Sir Geoffrey Howe said without elaboration, "For some time, we have had firm evidence of direct Libyan involvement in the kidnapping of Mr. Douglas and Mr. Padfield, and we have good reason to believe they were in Libyan hands."

Attorney General Edwin Meese said the United States "will look at the evidence" behind the killings. "But I think we won't announce in advance what we're going to do," he added.

Pentagon sources said the U.S. 6th Fleet remained "at a high state of readiness," steaming in the central Mediterranean north of the Libyan coast. But the sources added that the fleet, led by two aircraft carriers, had not received any orders to prepare for combat.

"But we are prepared for [Khadafy's] response and we will react depending on what it is," said Taft, who was interviewed for a Voice of America program.

Tim Kilburn, a nephew notified by the State Department, blamed the U.S. bombardment of Libya for his uncle's death. "We're on our way to war, as far as I can see," he said in Aptos, Calif. "The United States government's answer to problems is to drop bombs."

Vietnamese Foreign Minister Nguyen Co Thach said yesterday in New Delhi, India, that talks on 1900 U.S. soldiers missing in action had been called off until the U.S. military threat against Libya ends.