HAVANA, Cuba (AP) _ Prominent human rights activist Samuel Martinez Lara and nine other Cubans were arrested hours after an underground newsletter came out criticizing government policies, another activist said Thursday.

The 10 were arrested late Wednesday afternoon, and by Thursday all but Martinez Lara and three others were released, said Elizardo Sanchez, president of the Cuban Commission on Human Rights and National Reconciliation.

Martinez Lara is secretary-general of the Pro-Human Rights Party of Cuba and is a Sanchez ally.

Sanchez said the four were promised a speedy trial, which normally means a fine or several months' detention.

The arrests followed distribution of a two-page newsletter, Franqueza (Frankness), published by Martinez Lara.

Martinez Lara noted the scheduled visit this Sunday of Soviet President Mikhail S. Gorbachev - the first visit here by a Soviet leader in 16 years - and drew a comparison between modern-day Cuba and the era when the Soviet people had to wear ''a Stalinist muzzle.''

Sanchez said Martinez Lara is a psychiatrist who was imprisoned twice previously. He was convicted in 1982 for trying to leave the country illegally and served a three-year prison term, and later drew a four-month term starting in late 1986 as part of a general crackdown on dissidents, Sanchez said.

He reported that Martinez Lara's organization has hundreds of members.

Two days ago, the groups headed by Sanchez and Martinez Lara joined forces with a third organization to coordinate human rights activities. Sanchez said the new group represents more than 90 per cent of Cuban human rights activists.

The group, Umbrella 4970, said in a statement Tuesday it welcomes Gorbachev's visit, describing him as ''one of the great social reformers of our time.''

While stopping short of making an appeal to Gorbachev, the statement said previous Soviet governments contributed to the establishment in Cuba of ''oversized repressive machinery ... (at a) high human cost for our people.''

The Cuban government under President Fidel Castro has long maintained it has an exemplary human rights record. It contends that few countries can match Cuba's performance in providing eduation, health care and employment opportunities for its people.

Castro and hundreds of thousands of Havana residents are expected to greet Gorbachev on Sunday.

''Probably never before in the history of humanity have there been such fraternal relations between such a powerful country and such a small one,'' the Cuban Communist Party newspaper Gramma said in an editorial Thursday.

Rolando Cairo, Communist Party leader of Havana Province, said 612,000 people promised to turn out Sunday to greet the Soviet leader.

Gramma quoted Victor Volki, director of the Soviet Academy of Sciences, as saying the visit is to demonstrate ''the determined support of the Soviet Union for Cuba against any attempt against the right of its people to march down its chosen path.''

Leonid Brezhnev in 1973 was the last Soviet leader to visit Cuba.

Gorbachev and his wife Raisa are scheduled to stay three days in Cuba.