WINDHOEK, South-West Africa (AP) _ Major black trade unions in this South Africa-ruled territory said today they plan a two-day general strike to protest security force policies.

A newspaper editor was reported detained today under a proclamation allowing detention without trial.

The unions, representing an estimated 60,000 workers, said in full-page newspaper advertisements that the strike will take place Monday and Tuesday unless their demands are met.

The demands include the release of detainees, withdrawal of police from black townships, and the relocation of security force bases that are next to schools in the northern war zone.

South-West Africa, commonly known as Namibia, was been administered by South Africa since World War I. South Africa has defied calls by the United Nations to grant independence to the territory, saying it would consider doing so only after Cuban troops withdraw from neighboring, Marxist-ruled Angola.

Today marked the third anniversary of the installation of a multiracial interim government in Namibia, where blacks make up nearly 90 percent of the 1.3 million population.

The chairman of the transitional Cabinet, Andrew Matjila, said the planned general strike and an ongoing classroom boycott by many black students were part of a campaign to create insecurity in the territory.

''We have no intention of letting events slip out of our control,'' said Matjila, who is black.

The unions organizing the strike are affiliated with the South-West African People's Organization, Namibia's largest independent movement. It is a legal political organization in Namibia, but its guerrilla wing is outlawed and has waged a bush war in the north since 1966.