NAIROBI, Kenya (AP) _ Masinde Muliro, a Kenyan opposition leader instrumental in bringing multiparty politics to this African nation, died Friday at Nairobi's international airport.

Muliro, 70, had a heart pacemaker implanted several years ago, but the cause of his death was not immediately known, a family spokesman said.

He had just arrived from London, where he had spent three days on party business.

Muliro was vice chairman and charter member of the Forum for the Restoration of Democracy, which played a key role in persuading President Daniel arap Moi last year to open Kenya's single-party system.

Mwai Kibaki, Moi's vice president for 11 years and current head of the opposition Democratic Party, described Muliro as a ''fearless fighter for freedom and a man of impeccable integrity.'

A member of the large Luhya ethnic group in western Kenya, Muliro had been active in politics and government for four decades.

He served in parliament from 1957, six years before Kenya gained independence from Britain, until 1979. He returned to parliament in 1983, serving until he was again defeated in 1988.

Personality differences and power struggles have splintered the Forum since it was legalized, and Muliro, though remaining loyal to the Forum's aging leader, Oginga Odinga, had tried to help mend the rift.

Odinga mourned Muliro as a ''promoter and defender of democracy.''