MOSCOW, JULY 2 -- Karl Linnas, convicted in the Soviet Union of Nazi war crimes and deported from the United States to face a Soviet firing squad, died in a Leningrad clinic today, the Tass news agency reported.

Tass said the 67-year-old Linnas, accused of being a concentration camp director in World War II, died at 11:45 a.m. of heart failure after undergoing two operations. The exact nature of the operations was not made clear in the news reports.

The state news agency called the case "another warning to the countries which shelter Nazi war criminals," and suggested that Linnas died unpunished. It complained that U.S. officials delayed 26 years before deporting Linnas, a retired land surveyor from Greenlawn, N.Y.

A Soviet court in 1962 convicted Linnas in absentia and sentenced him to death. Witnesses said he supervised the killing of thousands of inmates, mostly Jewish women and children, at the Tartu concentration camp in Nazi-occupied Estonia. He was deported from the United States on April 21.

Tass said Linnas suffered numerous ailments, including heart disease, circulatory problems, internal hemorrhaging and cirrhosis of the liver.

"Linnas had fallen seriously ill way back in the United States but no thorough medical examination had been made there," Tass said.

Linnas had been allowed a visit by his daughter, Anu, and his defense attorney, former attorney general Ramsey Clark, a day before his death. Tass said the visitors "expressed satisfaction with the medical aid being given by Soviet physicians."

{In Los Angeles, Tony Manaka, a spokesman for the Coalition for Constitutional Justice and Security, said Linnas' death in the Soviet Union "leaves a cloud of suspicion and doubt about a number of things," such as "the cause of his death" and the "U.S. role in guaranteeing" that he could find no "safe haven" after being deported.

{"When he left (the United States) he was in good health," said Manaka, whose organization has sought legislation to safeguard due process for accused war criminals and opposes "involvement of the Soviet Union in our judicial process."}

In New York, U.S. Attorney Rudolph W. Giuliani, who argued twice before the federal appeals court in Manhattan to have Linnas deported, had no comment on his death. But he said the record against Linnas contained "proof to a certainty that he was a mass murderer and a butcher."

Linnas was moved to the Leningrad clinic last week from a prison in Tallinn, the capital of his native Estonia, where he had been jailed since his deportation. He had been awaiting a decision from the Soviet government on his request for a pardon.

Linnas was stripped of U.S. citizenship in 1982 for giving false information to immigration authorities when he entered the United States after World War II. He claimed to have been a displaced person and failed to disclose his role as administrator of the camp.

"He staged and conducted mass executions of Soviet citizens and personally took part in them," Tass said at the time of his deportation. "Linnas was involved in the killing of 12,000 people."

After losing his U.S. citizenship, Linnas waged a legal battle against deportation, but the Supreme Court ruled 6-3 in April against issuing a stay. He told reporters at Kennedy airport that U.S. authorities were participating in "kidnaping and murder" by sending him to the Soviet Union, and he struggled with his captors as they led him onto the aircraft.