FOUR African stowaways who arrived in Hong Kong on board a cargo ship at the weekend are being kept locked in a cabin while the authorities try to grapple with the complicated procedure of repatriating them. The two South Africans and two claiming to be Angolans sneaked on board the Dubai-registered Jilma in Cape Town on April 7. Two days into the voyage they declared themselves to the ship's captain, Rajeev Seth. Authorities in Singapore refused to help and on Saturday the 10,000-tonne steel-carrying vessel owned by the United Arab Shipping Company docked in Hong Kong. The two South Africans are to be repatriated tonight after their consulate in Hong Kong verified they were South African citizens. But the Angolans, who hold United Nations refugee certificates, will have to sail with the ship until a way of getting them ashore somewhere can be worked out. As neither has requested asylum in Hong Kong, the Immigration Department has refused them access. The difficulty of verifying their nationality and refugee status means they will likely stay on board when the ship sails for Taiwan tonight. Under international law, the captain is responsible for anyone on his ship, and must take care of his unexpected guests while on the high seas. ''All I can do is appeal to the various authorities to co-operate and sort this out as quickly as possible,'' he said. The Hong Kong representative of the ship's owner, Captain Clay Wild of Vart Matthews and Company, said there were tremendous difficulties concerning the repatriation of stowaways. ''Firstly, you have to verify their nationality, which in a country like Angola is difficult. You then have to arrange a direct flight, or inform the stopover country, who may refuse to allow them passage. ''We have a further problem here that two are claiming to be refugees. If they are, we have to find a third country that will take them.'' The cost of the repatriation will be borne by the ship's owner. Both the South African Consulate in Hong Kong and the United Nations High Commissioner for Refugees are assisting.