London — Even as it faces wide condemnation for shooting down the unarmed civilian Korean Air Lines jet, the Soviet Union is embroiled in another highly embarrassing situation here in London.
The most famous Soviet theatrical figure since World War II, Yuri Lyubimov, here to direct a play based on the Dostoyevsky novel ''Crime and Punishment,'' has clashed with senior Soviet Embassy officials over Soviet censorship within the USSR.
In a move that looks like defiance of Moscow, he has decided to stay in the West for an extra month, and the British have extended his visa here.
The Christian Science Monitor has also learned that Lyubimov has asked the British Foreign Office to give him physical protection while in London because he fears for his safety from Soviet agents.
It is possible that Lyubimov, who has made an international reputation as artistic director of the politically daring Taganka Theater in Moscow, may even defect to the West. Contrary to rumors sweeping London's theatrical world, however, he has not yet asked for asylum.
Defection of a theatrical figure of his eminence, a man known in a number of Western European countries for directing opera as well as plays, would be the biggest blow to Soviet artistic prestige since Rudolf Nureyev defected in Paris in 1961.
Through an intermediary, Lyubimov has confirmed to the Monitor that he has asked for his British visa to be extended from its expiration date of Sept. 13.
He declined to be interviewed. A spokesman for the Home Office, which handles visa procedures, confirmed that the visa had been extended until mid-October. A Foreign Office spokesman confirmed that Lyubimov ''has asked for some assistance.'' The spokesman would say no more: ''It would be inappropriate to go into detail,'' he said.
It was clear that the situation was sensitive and delicate.
The Home Office spokesman added that no request for asylum had been received.
One interpretion of Lyubimov's maneuvering is that he is bargaining with Soviet authorities for greater artistic freedom in his Taganka Theater.
Strengthening his hand is the presence of his Hungarian wife Katalin and his four-year-old son Petya in London with him, free from persecution back home.
By extending his visa, he is saying, in effect: ''I'm not returning to Moscow until I am assured I can be true to my own artistic integrity and my own company.''
In recent years Lyubimov has clashed constantly with censorship watchdogs of the Soviet Ministry of Culture.
The small, shabby, self-financing theater on Taganka Square in Moscow that he founded in 1964 has just been replaced with a larger, modern, but state-subsidized building next door containing three separate auditoriums. To Lyubimov's anger and frustration, the last three plays he has tried to stage there have been canceled by Communist Party officials before production.
Lyubimov is a tall, shaggy figure with tousled gray hair. He has been in poor health in recent years and blames his condition on constant harassment by Soviet censors. He is renowned for his constant battle to direct works that defy the demand of ''socialist realism'' for Marxist-Leninist ideological moralism.
When he talked to a reporter for the London Times recently, a Russian Orthodox cross hung from a chain around his neck. He affirmed both that he was baptized and that he considered himself a Christian today.
His clash with the Soviet Embassy here began after the Times interview, which took place some weeks ago and was published two days before the Sept. 7 premiere of ''Crime and Punsishment'' at the Lyric Theater in Hammersmith (Greater London).
Lyubimov used the interview to vent his feelings in trenchant, biting words that amounted to a declaration of independence from Moscow.
Lyubimov told the Times: ''I cannot accept this (the cancellation of the three plays in Moscow).''
The first banned performance was a tribute to his most famous actor, the late Vladimir Vysotsky, who was to Russians a mixture of what Laurence Olivier and the late Janis Joplin represent to the West - part superb actor, part iconoclastic superstar.
The second was a satirical play called ''Alive.'' The third was Pushkin's famous play called ''Boris Godunov,'' which is normally a Communist Party favorite.
Lyubimov, however, had made a telling change. In the play a Russian nobleman rebukes a crowd by asking it, ''Why do you do nothing?'' In the Lyubimov version , the same actor, out of costume, walks down into the stalls after the play and asks the audience: ''Why do you remain silent?''
Lyubimov told the Times: ''Neither I nor the theater can imagine continuing our work without these three productions. Without them I cannot work. I cannot allow myself to be trampled underfoot.''
At another point he said:
''I am 65 years old and I simply don't have time to wait until these government officials finally arrive at an understanding of a culture that will be worthy of my native land. . . . Most recently I feel that their decisions do not contribute to the cultural prestige of my country. . . . The majority of applications for my theater to work abroad have been denied.
''Every time I go abroad it is a complex, tense, and humiliating experience.''
Because of the article, Soviet Ambassador Viktor Popov refused to attend the premiere of ''Crime and Punishment,'' which has been hailed by three of the four major daily newspaper drama critics here as a brilliant evening of imaginative, unorthodox, and stimulating theater.
The following day he was visited by the embassy press counselor, Mr. Filatov. The exchange was an angry one.