Tension mounted here tonight over kidnaped U.S. Brig. Gen. James Lee Dozier following two contradictory telephone calls about his fate.

In Beirut, a caller speaking perfect Arabic and identifying himself as a spokesman of "the Red Brigades of the Baader-Meinhof," telephoned the local office of the Italian news agency ANSA this afternoon saying, "The Red Brigades claim responsability for the death sentence and execution of the American general, James Dozier, found guilty by a people's tribunal," the agency reported here.

"The corpse of the American pig is in a country village and the police will find it after 8 p.m.," continued the caller, who said he made the phone call in Beirut because of instructions designed for "greater security."

The Red Brigades are an Italian terrorist group that has kidnaped and murdered many prominent people, including former prime minister Aldo Moro. The Baader-Meinhof group is a West German terrorist organization.

Interior Ministry officials said they did not consider the Beirut message reliable. The caller also made the point of disassociating the Red Brigades from the 1978 kidnaping of the Shiite Lebanese Moslem leader Moussa Sadr. In the past, Red Brigade kidnapings have led to hoaxes such as one in 1978 when, weeks before Moro was murdered, police were sent vainly flying to a lake outside Rome where, a written message said, his body had been dumped.

Early yesterday the ANSA office in Bonn also received a nearly incomprehensible telex message in English addressed to "China Cooper and Dr. Trimble care of the audio-optical division Washington" and signed "condolences for and from another victim, James Lee Dozier."

One Italian government official described that message as "a macabre joke." But he admitted that the prolonged silence of Dozier's kidnapers did increase concern. Although the Red Brigades follow no strict time schedules, in previous kidnapings they have often released a photo of the hostage after only a few days. In the case of Moro, the Red Brigades sent a photo to the press two days after they kidnaped him.

In communiques found at two locations yesterday, the kidnapers said Dozier would be subjected to a "people's trial" and described him as a "Yankee pig." The kidnapers are not known to have made any specific demands for his release.

Dozier is deputy chief of staff for logistics and administration at NATO's southern Europe land forces headquarters in Verona.

An Interior Ministry official said the 50-year-old Vietnam War veteran might have been seriously hurt during the kidnaping. Mrs. Dozier has told investigators that her husband was hit over the head, apparently with a pistol butt. And, the Interior Ministry official confirmed, a lot of blood was found in the couple's apartment.

Some Italian and American officials here said that if the Dozier kidnapping should mark a shift in Red Brigade operations toward an anti-NATO drive, greater attention will have to be paid to the security and protection of NATO bases and personnel.

Nine of 14 commands belonging to the allied forces in southern Europe are located in Italy. About 12,000 U.S. troops are based in Italy, along with 700 additional American officers assigned to NATO here.