OSLO, Norway (AP) _ A Norwegian journalist on leave from his newspaper to work for humanitarian organizations was killed in the Ethiopian civil war, a Foreign Ministry spokesman said today.

Viggo Gilberg of the newspaper Fredrikstad Blad apparently was killed last week when the Eritrean Popular Liberation Front attacked the city of Afabet, ministry spokesman Lasse Seim said. Afabet is 95 miles north of Asmara, the provincial capital of Eritrea.

The rebels have been fighting for independence for Eritrea since 1962, when it was incorporated as a province of Ethiopia.

The Eritrean Popular Liberation Front said it crushed three infantry divisions of government troops and captured three Soviet advisers in what it described as its biggest victory in the war.

Soviet officials in Moscow said Tuesday that the Eritrean separatists had taken three Soviet military advisers prisoner last week and that a fourth Soviet was missing.

Gilberg, 31, was working for the Star of Hope and the Eritrean Relief Association when he was caught in the fighting, the national NTB news agency reported.

''Gilberg was killed while following a relief transport of food, medicines and blankets into a war zone where he knew there had been fighting recently,'' the agency said.

Seim said news of Gilberg's death reached Norway on Monday from the Eritrean Relief Association. He said Norway had no details about the situation and could not confirm the circumstances of the journalist's death.

Norway's nearest diplomatic mission is in Nairobi.

NTB said Gilberg had visited Africa several times before, including a recent visit to Mali to report about relief work there by the Church's Emergency Aid.