Prime Minister Robert Mugabe's ruling political party tonight was on the verge of a sweeping victory in an election that could pave the way for his stated goal of turning Africa's newest nation into a one-party state.

Results announced early Saturday showed Mugabe's Zimbabwe African National Union winning 57 of 79 seats at stake, Reuter reported.

In the southwestern Matabeleland region, opposition leader Joshua Nkomo's party won 12 seats and appeared to be winning the remaining four.

The vote reflected the deep political and ethnic cleavage between Matabeleland, home of Nkomo's Ndebele minority, and the Shona-speaking majority in the rest of the country.

Black voters went to the polls for four days this week in the first election since independence in 1980 to select legislators to fill 79 seats in the 100-member Parliament. The race for the 80th black seat was postponed folowing the death of one of the candidates.

Zimbabwe's small white minority voted last week for the other 20 seats in a special whites-only poll that gave a surprise victory to former prime minister Ian Smith, a longtime opponent of Mugabe. Smith's party took 15 of the 20 seats.

The black turnout of nearly 3 million voters was a sign of the enthusiasm with which voters here greeted the opportunity to go to the polls.

Mugabe began this campaign playing down his long-stated goal of moving Zimbabwe toward becoming a one-party state.

But in recent days the theme has reemerged in campaign speeches, with Mugabe saying yesterday that he would give opponents "a last chance" after the election to join his ruling party voluntarily. He warned that the government would take "sterner measures" against those who refused his offer.

Under the country's constitution, Mugabe cannot legally transform Zimbabwe into a one-party state until 1990 short of a unanimous vote in Parliament.

The prime minister has pledged in the past to honor the constitution but has grown increasingly critical of the document in recent days following Smith's upset victory.

The constitution grants whites 20 seats until at least 1987 despite the fact that they make up less than 2 percent of the population.

Mugabe won easy reelection in his suburban Harare district, and most of his senior Cabinet ministers also were reelected easily.

Two exceptions were Enos Nkala and Callistus Ndlovu, Ndebele-speaking members of Mugabe's Cabinet and ruling party, both of whom were perceived as turncoats by voters in their Matabeleland districts.

Nkala received only about 10 percent of the vote and Ndlovu less than 5 percent, with both losing to candidates of Nkomo's Zimbabwe African People's Union.

Another electoral casualty was Methodist Bishop Abel Muzorewa, who served as prime minister in a short-lived biracial governmment that preceded the internationally negotiated independence accord in 1980. Muzorewa, whose party held three seats in the last Parliament, was overwhelmed in his district outside Harare, winning less than 10 percent of the vote against the candidate of Mugabe's party.

Muzorewa, who spent 10 months in detention without charge last year left the country earlier this week, reportedly for Malawi. Supporters here said he left for "security reasons."

Election officials extended the balloting, originally scheduled to end Tuesday night, by two days, to cope with the size of the turnout and the slowness of the voting process. Voters waited in lines, some more than a mile long, for up to two days to cast their ballots.

In Matabeleland, the scene of political unrest and government crackdowns on civilians allegedly linked to armed dissidents, there were no roadblocks and little evidence of the Army during the polling. Most voting stations were guarded by a handful of lightly armed police who confined their duties to crowd control.

Alois Maveneka, spokesman for the Catholic Justice and Peace Commission, a church-sponsored human rights group whose members monitored the voting process, said the commission was satisfied with the poll.

"Our observations have satisfied us that this election exercise has been conducted by the government, the police and the electorate in such a manner and in such an atmosphere of discipline and peace that every Zimbabwean should regard it as having been free and fair," Maveneka said.