Soviet police fought a pitched gunbattle yesterday in downtown Moscow with a man armed with a sawed-off shotgun. The gunman had taken hostages in the Finnish airlines office and demanded a plan to take him abroad.

The police captured the man after firing a fusillade of pistol shots and tear gas cannisters through the shattered front window of the street level office two blocks from Red Square.

Soviet sources identified the assailant as Mikhail Timoshukov, 22, and said he was an escaped prisoner from Kazakhstan. He said he represented the "Russian Liberation Army."

Such a shootout is virtually unknown here, where ownership of guns is sharply restricted. The fact that Western correspondents heard about it in time is also remarkable since out-bursts of violence here are carefully and effectively screened from foreigners.

Two newsman, Bernard Redmont of CBS and Charles Bremner of Reuter news agency were detained briefly by Soviet security agents until Redmont gave up film he had made of the Finnair office after the assailant was taken away by the police. The KGB agents also yanked a camera from Douglas Stanglin of UPI and removed and exposed the film.

The successful police assault, in which no one was injured began after the hostages, Finnair secretary Ludmilla Semyonova, and Finnish Embassy driver Sergei Zubkov, raced out of the office while Timoshukov apparently was reloading his double-barreled weapon. With the hostages free, the police opened fire while Timoshukov fired back from inside.

According to an eye witness, there were at least eight shots from inside while the police fired more than two dozen times from behind a van they had parked next to the office. Timoshukov stumbled out after police fired three or four tear gas cannisters. The whole incident lasted about 95 minutes.

It began about 12:40 p.m. according to Semyonova, when a man wearing a dark hood over his face walked into the Finnair office and brandished the gun. It was a warm spring day here yesterday and the sidwalks were filled with people shopping and strolling in the sun.

The assailant said he wanted a plane to fly abroad. Within moments, Semyonova called the Finnish Embassy and reported the situation. The Finns called Soviet police and the Foreign Ministry and began communicating with their own government in Helsinki.

Embassy security chief Juhani Vaananen and three guards drove to the Finnair office. Finnair is one of the few Western concerns here with an office on the street. Soviet police arrived a few minutes later and set up barricades around the front of the small building and moved passersby off the street.

During the next hour, Timoshukov made several phone calls to the Finnish Embassy, threatening the hostages unless he got a plane.

At one point, the assailant told UPI that he was from the "Russian Liberation Army," a group unknown to Western diplomatic and other sources here. A group with such a name was formed during World War II under former Soviet General Andrei Vlasov and fought briefly alongside Nazi German forces against the Red Army in the last months of the war. Its units were comprised in part by Russians who had been captured, like Vlasov, by the Germans.

Finnish Embassy spokesmen declined to say if the man's telephone calls to them contained any political content or statements. Their closed-mouthed attitude reflects the delicate relations between Finland and its powerful Eastern neighbor.

The assailant fired several times through one of two large plate glass windows of the office, but police bided their time until Zubkov and Semyonova escaped. Then the heavy firing began.

The incident attracted the attention of Gen. Boris Shumilin, a top-ranking officer of the Interior Ministry.

Semyonova, 40, was slightly injured when she rushed from the office as her captor was reloading. In a disjointed conversation with a correspondent, she said she fought with the man before escaping, but she gave no details. She indicated she had wrenched her leg while fleeing.

The last known shooting incident in Moscow was in 1969, when a man later said to be a disgruntled Soviet officer fired several shots at a motorcade carrying Soviet leader Leonid Brezhnev, some of his top associates and a group of Soviet cosmonauts. A driver and a policeman were killed in the shooting that took place at the Borovitsky Gate to the Kremlin.

Other violent incidents here involved several hijacking attempts. In one successful hijacking an Aeroflot stewardess was killed.

Yesterday's incident was reported briefly by the official news agency Tass, which described Timoshukov as "an unknown Soviet citizen." Soviet sources who identified him said they have obtained his name from Moscow police.