Deposed president Ferdinand Marcos today refused on grounds of Philippine national security to answer questions about the 1981 slayings of two Seattle labor officials who opposed his regime, the plaintiffs in a civil suit said.

Marcos refused even though an attorney for the government of Corazon Aquino, who replaced Marcos, had no objections to Marcos' answering, according to Terri Mast, a widow of one of the men.

Facing his first questions under oath since arriving in Hawaii in February, Marcos said he still considers himself president of the Philippines, but even as a "concerned citizen" would not answer questions that he thinks would jeopardize that country's security, Mast said.

Attorneys for Mast and others are expected Tuesday to ask a federal judge here to order Marcos to answer the questions or be cited for contempt. Attorneys for the estates of Silme Domingo and Gene Viernes, the slain men, questioned Marcos for more than two hours this morning on the beach front lanai of his rented home here. The videotaped deposition was sealed under court order at Marcos' request, but Mast, who was present during the questioning, later talked with reporters.

She said Marcos was alert, polite and made "a lot of speeches" in answering biographical and historical questions.

Heirs of Domingo and Viernes, who were active in the Marcos opposition in this country before their murder in Seattle in 1981, claim that agents of Marcos' government conspired to violate the civil rights of the two men, leading to their deaths. Lawyers in the case seek to question Marcos about the activities of Philippine intelligence agents in this country while he was in power.

Three Philippine expatriates were convicted of first-degree murder in the Seattle slayings and sentenced to life in prison.

Marcos and his wife were dismissed as defendants in the $30 million civil suit in 1982 when a judge ruled they had "head-of-state" immunity. However, another judge ruled last month that Marcos can be questioned in the case.

Marcos first raised the national security objection today when asked about his intelligence training in the Philippine armed forces in 1937, Mast said. He objected again when asked about Philippine intelligence operations in the United States.