JOHANNESBURG - Angola's ruling MPLA party has won 191 of the 220 seats in parliament, cementing an election victory critics say could herald a slide back towards authoritarian rule.

In power since independence from Portugal in 1975, the MPLA won 81.64 percent of votes cast in the September 5-6 poll versus 10.39 percent for UNITA, the former rebel group and largest opposition party, the electoral commission said late on Tuesday.

MPLA officials have signalled that some senior UNITA officials in the government will be removed and that there will be changes to the constitution but have rejected suggestions the party will use its muscle to re-establish a one-party state.

It was the first election to be held in Angola in 16 years and came six years after the end of a 27-year civil war in 2002. The conflict killed half a million people and destroyed much of the country's infrastructure.

Angola has rebounded on the back of an oil-fuelled boom and the MPLA, which abandoned Marxism in the early 1990s, has wooed investors. The economy grew 24 percent last year.

The government is keen to lure more foreign investment into its booming oil and diamond sectors as well as other neglected areas, including agriculture. Observers say a consolidation of MPLA power is unlikely to scare off investors.

"The stigma of war, which had been tied to the elections, is finally banished. We are turning the page of uncertainty," Caetano de Sousa, president of the National Electoral Commission, told a news conference in Luanda.

UNITA, which held 70 seats going into the election, will be reduced to 16 in the next parliament. A handful of smaller parties will divide the remainder.

UNITA accepted the result but complained the MPLA's access to funds and wide control over the media put it at a serious disadvantage in the vote, a charge backed by U.S.-based Human Rights Watch in a statement this week.

"With presidential elections due in 2009, Angola needs to reform the electoral commission so it isn't dominated by the ruling party and can respond effectively to election problems," said Georgette Gagnon, the group's Africa director.

U.S. and European election observers agreed the playing field was not level and the poll was marked by irregularities, but said it represented a step in the right direction for a country emerging from decades of war.

Until the collapse of communism in the early 1990s, the MPLA operated a virtual one-party state that was aligned to the Soviet Union and its allies.

Joint parliamentary and presidential elections in 1992 ended in disaster when UNITA leader Jonas Savimbi boycotted a second round of the presidential poll after accusing President Jose Eduardo dos Santos of cheating his way to victory.

UNITA resumed its bush war against the government, only agreeing to lay down its arms after Savimbi was killed in 2002.