MASAYA, Nicaragua (AP) _ Government supporters chanted ''people power 3/8'' and hurled rocks as they broke up a protest march by 1,000 people calling for an end to the military draft and new austerity measures.

At least four people, including two opposition figures, were injured during the incident Sunday in Masaya, 20 miles southeast of the capital of Managua.

It could not be determined if police had made any arrests.

In a statement released Sunday night, the Interior Ministry charged that opposition protesters provoked the melee.

Erick Ramirez Benavente, president of the opposition Social Christian Party, told The Associated Press that supporters of the leftist Sandinista government took him inside a house and beat him during the confrontation.

''The aggression suffered today by the opposition parties shows that the Sandinista National Liberation Front is not willing to concede any degree of liberty in the country,'' Ramirez Benavente said. ''It is willing to repress any opposition demonstration.''

One government supporter was injured when his own colleagues mistakenly took him for a demonstrator and hit him repeatedly with clubs.

Witnesses said there were more injuries, including a young boy who was wounded in the face. Nicaraguan Red Cross officials treating the injured nearby declined to give details and denied access to journalists.

A vehicle close to the theater that was owned by Ramirez Benavente was overturned and set afire by the pro-Sandinistas, who also damaged two other vehicles belonging to the opposition Social Christian Party.

The witnesses said that groups of thugs like the ones they encountered are often called out to break up anti-government demonstrations.

The anti-government march was sponsored by the Nicaraguan Democratic Coordinate, the country's main opposition group, to protest the military draft and new economic measures that boosted prices and scrapped the old cordoba currency as part of an inflation-fighting program.

The protesters also called for amnesty for political prisoners.

After dispersing the march, the Sandinista supporters gathered in front of the Masaya theater, where Federico Lopez, a government delegate for four eastern provinces, addressed the crowd.

He said ''the enemies of the people, in the pay of the American Embassy and the CIA,'' had sought to take over city streets.

The Interior Ministry statement said ''demonstrators of the Nicaraguan Democratic Coordinate assaulted with rocks a 13-year-old minor, Bryon Zambrana Selva, which provoked the reaction of'' pro-Sandinistas.

The statement said that several people were injured, ''among them Erick Ramirez Benavente'' and coordinate activist Auxiliadora Mendoza.

Police went to the scene to ''give protection to the demonstrators of the coordinate'' and ''to reestablish public order in the city,'' it said.

There were violent demonstrations in Masaya against the draft in early February. About 800 demonstrators belonging to the Democratic Coordinate marched Saturday in Managua, also calling for an end to the draft.

The influential Roman Catholic Church also has come out against the draft.

Young men 18 years of age have been required since 1983 to serve in the military. Many draft-age men in recent years have sought to avoid military service, moving to parts of the country other than where they are registered.

Masaya has been a Sandinista stronghold since 1978 when it was one of the most important points in a series of uprisings against Anastasio Somoza, the rightist, pro-American strongman overthrown in July 1979 by the Sandinistas.

Under a 1982 state of emergency law, public protests in Nicaragua were illegal unless government permission had been obtained. President Daniel Ortega lifted the law in January as part of efforts to comply with a regional peace plan signed last August in Guatemala City.

Since then, opposition groups have mounted rallies and marches to protest government policies.