JOHANNESBURG, South Africa (AP) _ Security forces in the black homeland of Ciskei captured more of the commandos who attacked the president's house and were seeking a Frenchman suspected in the assault, according to news reports today.

The Ciskei government says the attack before dawn Thursday was carried out by soldiers from Transkei, another nominally independent black homeland separated from Ciskei by a strip of South African territory.

Transkei's foreign minister, Caleb Songca, said Thursday his government knew nothing about the attack. Transkei Prime Minister George Matanzima was to hold a news conference later today.

The South African Broadcasting Corp. reported today that four more of the attackers were captured during an intensive search around the Ciskei capital of Bisho.

The chief government spokesman, Headman Somtunzi, said one of the 23 attackers was killed during the brief clash and two were captured immediately, one of whom was seriously injured.

Ciskei President Lennox Sebe and his family were not hurt in the assault.

Somtunzi said Ciskei authorities were looking for a Frenchman, identified as Michael Desbele, who had visited Ciskei before the attack and said he planned to write a book about the homeland. The car used by Desbele was one of three vehicles used by the attackers, Somtunzi said

Business Day, a Johannesburg daily, reported that Desbele was a professional soldier who served in the Rhodesian army during the civil war there that ended in 1980 with the black majority taking power. The country is now Zimbabwe.

The Citizen, a Johannesburg daily, quoted unidentified South African intelligence sources as saying they had confirmed Transkei's involvement in the attack. Somtunzi said the attackers planned to take Sebe hostage to force a merger of the two homelands, both populated by South Africa's Xhosa tribe.

South African Foreign Minister R.F. Botha said Thursday his government could not take sides in the dispute, but he warned Transkei it could not tolerate use of South African territory for attacks on Ciskei.

Ciskei has been feuding with Transkei for six months and announced Wednesday that all Transkeians in its territory must leave by Aug. 31.

Somtunzi said the attackers arrived at Sebe's residential compound in a disguised Transkei troop carrier, a jeep and at least one private car.

He said gunfire broke out, and guards killed a Transkei soldier and captured Maj. Nkosinathi Sandile, formerly Ciskei's military security chief, who was with the attack force.

Sandile said last month at a news conference in Transkei that he had been caught while leading a mission there to abduct Lt. Gen. Charles Sebe, the brother of Lennox Sebe who escaped in September from a Ciskei prison. Charles Sebe had been imprisoned in 1983 for allegedly plotting a coup against his brother, and sought refuge after his escape in Transkei.

Ciskei and Transkei are two of four tribal homelands designated as independent by South Africa but whose sovereignty is not recognized abroad. They border the Indian Ocean on South Africa's southeast coast, about 50 miles apart with the port of East London between them. Inland, as little as 15 miles separates them.

They are impoverished one-party states led by strongmen who cooperate with the white authorities in South Africa.