Guerrillas of white-ruled South Africa's black underground have made a series of armed raids on police stations in the neighboring kingdom of Swaziland to free comrades arrested there, Swazi police reported today.

In one raid the guerrillas forced guards to open the cells of the main police station in the capital of Mbabane and freed six members of the underground African National Congress held there, Police Commissioner Majaje Simelane said.

The commissioner added that armed police managed to fight off raids on three other police stations and prisons and that a nationwide search for the guerrillas was being mounted.

There have been intermittent skirmishes between the black South African guerrillas, who are trying to overthrow white-minority rule in their country, and the security forces in the little kingdom since the Pretoria government signed peace treaties with Mozambique and Swaziland early last year.

Until then, African National Congress fighters had used the southern Mozambique and Swaziland salient, which juts into eastern South Africa, as their main guerrilla trail into the white-dominated republic, the dominant military and economic power in the region.

Under the treaties, the two adjoining black-ruled countries agreed to prevent this -- Mozambique because of economic collapse and the depredations of South African-backed rebels and Swaziland because the death of its autocratic monarch, Sobhuza II, brought to power a group of conservative pragmatists willing to deal with their segregationist neighbor.

Sobhuza, who was the world's longest reigning monarch when he died in 1982, had managed to walk a tightrope. He was an honorary member of the African National Congress and quietly gave it access to his vulnerable little country, while at the same time maintaining good relations with his powerful white-ruled neighbor.

After his death this aid to the congress collapsed under South African pressure.

Trouble broke out in Swaziland after the signing of the treaties. Many congress guerrillas fought back as the little kingdom tried to deport and round them up in terms of its agreement with Pretoria. At the same time hundreds slipped into Swaziland across the border with Mozambique to escape deportation from there.

Several pitched battles were fought with the Swazi Army and police. In one, the assistant commissioner of the Royal Swazi Police Force was killed. In another, a group of 15 arrested guerrillas broke out of a prison and fought a running battle with Swazi soldiers through the suburbs of the capital last April.