SAN FRANCISCO, El Salvador (AP) _ Government soldiers rounded up 10 people from this village, accused them of collaborating with leftist rebels and killed them with grenades and rifle fire, relatives and neighbors said Thursday.

The killings Wednesday in San Francisco, a tiny farming town 30 miles east of San Salvador, appear to constitute the biggest mass slaying of civilians in this war-ravaged country in four years.

The Armed Forces Press Office reported earlier Thursday that 10 ''subversives'' were killed Wednesday just outside San Francisco.

It said troopers of the Jiboa Battalion ''surprised a group of extremists of the FMLN who were moving through the area.'' It described the confrontation as ''fierce combat.''

Marxist-led rebels of the Farabundo Marti National Liberation Front, or FMLN, have fought El Salvador's U.S.-backed centrist government for nearly nine years.

But more than 10 witnesses to Wednesday's incident interviewed by The Associated Press said there was no combat and that the 10 men and women killed had been taken from their homes or detained as they carried out chores or walked along village paths on errands.

Several of those interviewed by the AP were detained along with most of the village's inhabitants in the local schoolhouse. They said the three women and one of the men killed were taken from the schoolhouse and marched about a mile to a ravine where six other village men were detained.

Three explosions, presumably grenades, were heard at about 3:30 p.m. Wednesday, followed by a steady fusillade of rifle fire, the villagers said.

Local residents were prevented by the troopers from going the place of the killings Wednesday evening. The villagers found the bodies early Thursday morning.

An officer at the Armed Forces Press Office, asked about the villagers' version of events, said the armed forces had no further information to modify its earlier report. But the officer, who declined to give his name, said the matter would be investigated.

The 10 bodies were covered while still in the ravine with a banner proclaiming a slogan of the leftist guerrilla group.

Villagers put the bodies in hammocks Thursday afternoon and carried them to the local churchyard, where relatives mourned their dead. Some of the bodies were disfigured by explosions or shrapnel.

Relatives identified the victims as: Teresa Argueta, 47; Maria Zoila Rivas, 45; Maria Jesus Sibrian, 27; Jose Maria Flores, Jose Alfaro, Nicolas Alfaro, Francisco Alfaro, Ulises Sibrian, Jose Atilio Rivas and Jesus Zepeda.

The ages of the men were not known.

Maria Julia Argueta, Jose Atilio Rivas' common law wife, said five Jiboa troopers arrived at the family's adobe house at 5:30 a.m. Wednesday. She said they searched it thoroughly, then took her husband away and ordered her to remain inside with the couple's three children.

''They said they were going to give him a talk, that they did that whenever they went into a village,'' Mrs. Argueta, her eyes red from crying, told the AP in the churchyard.

Mrs. Argueta is also the sister of Teresa Argueta, one of the slain women.

Maria Gumersinda Melendez, 28, said she and her daughter, Blanca, were walking to the nearby town of San Sebastian when they were detained by the troopers at 6:30 a.m.

The two said they were held in the schoolhouse all day with about 35 of the village's approximately 70 residents, including about a dozen children. At mid-afternoon, the soldiers called the names of Ms. Argueta, Ms. Rivas and Ms. Sibrian along with those of Francisco Alfaro and Rosa Emilia Rivas.

The five stepped forward, were blindfolded and led out, they said. Rosa Emilia Rivas told the AP that she was released outside the schoolhouse, apparently because the soldiers realized they wanted Maria Zoila Rivas instead of her.

The women said the soldiers had a list of names from which they appeared to be working. They said different soldiers who addressed the detainees in the schoolhouse accused the villagers of supporting the front.

Rosa Emilia Rivas told the AP she believed she was being led out to be killed when she was taken from the school.

''They called us collaborators (of the guerrillas),'' she said.

''I don't feel safe here anymore. I would like to leave, but I don't have anywhere to go,'' she said.

''I feel a great fear about staying here,'' said Mrs. Argueta.

The last mass killing of non-combatants attributed to the army took place on Aug. 30, 1984 in the town of Las Vueltas in Chalatenango province. Thirty- four civilians were killed there, according to local and international human rights groups.

No officer or soldier was prosecuted for that atrocity.