Two police officers and two civilians, one a 3-year-old child, were killed last night when black insurgents attacked a police station in Bophuthatswana, one of South Africa's "independent" homelands.

All the victims were black.

Bophuthatswanan police declined to attribute responsibility for the attack, which occurred in the township of Mabopane, only 24 miles from South Africa's administrative capital of Pretoria. However, it follows a number of recent attacks on government facilities that have been the work of the banned African National Congress, a Soviet-armed insurgent organization fighting to break down South Africa's apartheid system.

Activities by these insurgents have increased markedly this year. The latest attack came only three weeks after rockets were launched on Voortrekkerhoogte, the South African military base in Pretoria.

South African military strategists have privately expressed concern that the homelands, where more than half of South Africa's 18 million blacks live in poor and crowded conditions, could become more susceptible to black insurgency.

This was the first attack on a police station in Bophuthatswana. Previously, isolated armed contacts between insurgents and police have occurred in the homeland's countryside as the insurgents attempted to infiltrate from the neighboring nation of Botswana.

In May a police station in the homeland of Ciskei, scheduled to become independent in December, was attacked. The head of the Ciskei police force was involved in a brief shootout with armed insurgents that same night.

The death toll of four, if indeed the work of congress insurgents, would be one of the largest number of casualties for a single attack by the group.

It points to the likelihood, as in the Zimbabwean conflict, that most of the victims of the insurgents' warfare would be blacks.

During last night's attack, a car approached the Mabopane police station about 9 p.m., according to a spokesman for Bophuthatswanan police. He said hand grenades were thrown into the station from the car. Then a group of armed men attacked the station with Soviet-designed AK47 rifles, he said.

Initial press reports said between 20 and 30 insurgents were involved, but Bophuthatswanan police later said they believe only four participated.

There were also conflicting press reports on exactly how the two police officers and the civilian adult died. The Johannesburg Star newspaper reported that the two policemen, one of whom was on guard duty, were sitting in a car outside the station and died when the vehicle was apparently hit by a grenade. Two charred bodies were seen by reporters and police in the car this morning.

But the South African Press Association reported that one officer died in the car and one was shot in the station. There was no explanation as to how the civilian was killed.

The child was in a house adjacent to the station, and was apparently wounded by gunfire. The child later died in the hospital.

South African police were immediately called in to help Bophuthatswanan police search for the insurgents.

The attack is likely to cause serious concern among black leaders who work within apartheid homeland structures in the hope of bringing about change through nonviolent methods. These leaders, such as Zulu Chief Gatsha Buthelezi, have publicly warned Pretoria that if fundamental changes are not made soon, the leaders will lose their credibility with their own people.