The Soviet government moved today to end a hunger strike by Andrei Sakharov, the country's foremost civil rights activist, by taking him to a hospital on the 13th day of his protest.

Indications here are that Sakharov and his wife Yelena Bonner, who had joined him on hunger strike, were involuntarily hospitalized in Gorki, an industrial city 250 miles east of here to which he was banished almost two years ago.

A cryptic statement in the government newspaper Izvestia said the Sakharovs were being administered "prophylactic medical assistance to prevent any complications in the state of their health." The phrase suggested they are being fed intravenously.

Sakharov, in a message a few days ago, asserted that he would not end his protest or seek medical help unless the government allowed a young woman to join his stepson in the United States. "Now the only possibility for terminating our hunger strike is the exit" of Liza Alexeyevna, the nuclear physicist said.

President Reagan publicly appealed to the Soviet Union to settle the Sakharov issue. See A19.

The brief statement in Izvestia tonight was coupled with a long commentary that sharply criticized Sakharov's past political activities, and asserted that he had gone on hunger strike in an effort to turn personal family problems "into a cosmic crisis."

Sakharov, who helped develop the hydrogen bomb, is one of the leading Soviet scientists.

There was no information about the state of the Sakharov's health. One of the physicist's acquaintances telephoned from Gorki tonight that the Sakharovs were not in their apartment.

Alexeyevna had sent a telegram early today to Sakharov and received an official confirmation from Gorki by midmorning that the cable had been handed personally to him.

Knowledgeable sources said earlier that because of their age, the Sakharovs' condition was likely to become critical after two weeks of fasting. Sakharov is 60, and his wife is 58. They have been taking only mineral water for the past 13 days.

But observers here said that the Sakharovs may not have been seriously affected by their hunger-strike regime, and that intravenous feeding at this point could bring them back to health in a few days.

Sakharov's latest message to Alexeyevna four days ago asserted that both he and his wife "are holding on cheerfully, we are following our regime."

When told by a journalist tonight of their hospitalization, Alexeyevna said, "I'm sure they did not go to the hospital voluntarily."

The apparently enforced hospitalization seemed to have been designed to head off a crisis and adverse headlines in the West.

But, as the Izvestia commentary indicates, Soviet authorities are going to use the occasion to discredit the physicist, who was one of the most honored members of the scientific establishment before falling from favor in 1968 for writing an essay critical of Soviet policies.

In what was the first mention of the hunger strike by the Soviet media, Izvestia said that it was a trick and a provocation "designed to attract once more the West's attention to Sakharov's anti-Soviet views and to play up to forces trying to undermine detente and aggravate international tension."

But the central theme of the commentary focused on the case of Alexeyevna in a way likely to find considerable resonance in Soviet society.

The paper said that Bonner's son, Alexei Semenov, while married to another woman, Olga Luvshchina, had an illicit relationship with Alexeyevna. Semenov was permitted to emigrate to the United States and Luvshchina and their child joined Semenov there under the provision of "family reunification."

"Alexeyevna was deserted," the paper said. "She tried to commit suicide but was saved by doctors." Subsequently Sakharov and Bonner took Alexeyevna into their apartment as a "maid" and "started to brainwash her."

The paper said that Alexeyevna, who is not Jewish, tried first to emigrate to Israel "at the invitation of a fictitious aunt." Her father, a retired lieutenant colonel, and mother both "categorically objected" to her plans for leaving the country.

Later, when her application was rejected, she used a "trick" devised by the Sakharovs. Semenov and Luvshchina were divorced in the United States and Semenov married Alexeyevna in a proxy ceremony in Montana. Izvestia said that Soviet laws allow "neither bigamy nor proxy marriages."

Much of the commentary was given to the objections of Alexeyevna's parents. The article was written in a way to titilate Soviet audiences, and subtly convey the impression that the physicist's difficulties had to do "with the discord in his own soul, troubles in the family life of Bonner's son and other relatives."

The article also included a list of charges against Sakharov. It quoted him as telling former senator James Buckley that the United States should use all means of pressure against the Soviet Union. It said that Sakharov had advocated the resumption by Washington of the arms race "until the United States is two or three times" more powerful than the Soviet Union.