An explosion in a crowded Moscow subway train over the weekend in which several persons died could have been caused by a terrorist's bomb, according to accounts circulating unofficially in Moscow today.

The Soviet News Agency Tass announced only that a "small explosion had taken place" in a subway car traveling near Izmailova Park in Moscoe's northwestern suburbs. The item said where were victims who were rendered medical aid." That terse report was later supplemented by Soviet sources - chiefly the journalist Victor Louis - who suggested that terrorism may have been involved.

Louis correspondent for the London Evening News, has often been used in the past to disclose sensational information that the Kremlin for some reason wants to reveal in the West, so his graphic explanation of the episode carries some weight. He flatly told a United Press International reporter who reached him by telephone late tonight that the blast resulted from a bomb."

"A bomb cannot be peaceful so it was clearly a terrorist's bomb", Louis said.

Any hint of violent political opposition in the Soviet Union 8 particularly coming from a prominent Soviet publicist like Louis - is stirking. There have been occasional reports in recent months of explosions and fires in Soviet Georgia attributed to nationalist extremists or private enterpreneurs angered by a crackdown on local corruption.

The last significant terrorist incident in the Soviet capital occured in 1969 when a man dressed as a Soviet army lieutenant fired several shots at a motorcade carrying four Soviet cosmonauts as it approached the Kremlin gates. The man was seized and later described in the Soviet press as a schizophrenic.

Details of the weekend explosion are scarce. Estimates of the number of persons killed rangee from three to seven with the number of wounded said to be as high as 20. A report from the West German news agency DPA said that three men were spotted placing a parcel on the subway.The blast was reported to have taken place between stations and Louis said that many of the passengers on the crowded train were children.

Why Moscow would wish to publicize a terrorist incident - if indeed that is what the explosion was - is something of a mystery. One possibility is that the affair could be used as the excuse for taking some stringent new measures against dissidents.

Louis said he thought the blast would produce "a violent public reaction" in the Soviet Union comparable to the reaction in Western countries against such terrorist groups as the Bader-Meinhoff gang in West Germany and the Symbionese Liberation Army in the United States.