The national Party of Nigeria, one of the country's three conservative parties, took a slight lead in senatorial election returns today, as the results of Saturday's voting continued to trickle out of the country's Electoral Commission.

With 63 of 95 Senate seats decided, the National Party, led by Shehu Shargar, had won 22 seats.

The populist Unity Party of Nigeria, led by lawyer-politician Obafemi Awolowo, had won 21 seats. The Nigerian People's Party, headed by former ceremonial president Nnamdi Azikiwe, was running third with 16 seats.

Millions of Nigerians went to the polls on Saturday to vote in the country's first election in 15 years. The vote was the first of five scheduled elections, each a week apart, leading to a presidential election on August 11.

The military government, which has ruled Nigeria since 1966, is scheduled to hand over power to the newly elected civilian government on October 1.

Poor communications and torrential downpours have slowed the release of the vote count. Final results are not expected until later this week.

The three leading parties, each supported by one of Nigeria's major ethnic groups, were expected to do well. The Unity Party enjoys broad support among the Yoruba in western Nigeria; the National Party among the Hausa-fulani in northern sections and the People's Party among the Ibos of eastern Nigeria.

Wealthy Nigerian businessman Waziri Ibrahim's Great Nigerian People's Party was running in fourth place with four senatorial seats. The proleftist People's Redemption Party, headed by Socialist Aminu Kano, had not been officially credited with winning any seats. The party was expected to do no better than five seats, according to one unofficial source.