Angola's chaotic first post-war vote "might not reflect the will of the people," the leader of the main opposition UNITA party said on Sunday after initial results gave a sweeping lead to the ruling party.

"The final result might not fully reflect the will that was expressed by the people of Angola in the ballot," Isaias Samakuva, leader of the Union for the Total Independence of Angola (UNITA) told a press conference on Sunday.

He would not say whether his party would formally contest the results, saying he would comment on that only after the final results are in.

With nearly half of the votes counted on Sunday, the ruling leftwing Popular Movement for the Liberation of Angola (MPLA), in power for more than 30 years, held a big lead with 81.65 percent of votes, according to the electoral commission.

UNITA trailed with 10.59 percent of the votes.

Despite Samakuva's comment, and criticism of chaos at some polling stations Friday that caused delays and forced the vote's extension by a day, the opposition leader was upbeat about the ballot.

"Our country (has) just made an important step towards consolidation of our democracy," he said.