Angolans will vote on Wednesday in a tight race in which the main opposition coalition has its best-ever chance of victory, as millions of youth left out of its oil-fuelled booms are expected to express frustration with nearly five decades of MPLA rule.

The ruling party remains favourite, though the margin is narrow enough for a surprise UNITA victory, which could shift relations with global superpowers -- with possibly less friendly ties with Russia.

Since independence from Portugal in 1975, Angola has been run by the formerly Marxist People's Movement for the Liberation of Angola (MPLA), led since 2017 by President Jaoa Lourenco.

But an Afrobarometer survey in May showed the National Union for the Total Independence of Angola (UNITA)'s opposition coalition, led by Adalberto Costa Junior, increasing its share to 22%, from 13% in 2019.

That's still seven points behind the MPLA, but nearly half of voters were undecided. Many youths -- under 25s make up 60% of the country -- are voting for the first time.

In a tense run-up to the vote for both president and parliament, UNITA has urged voters to stay near polling stations after voting to reduce the risk of fraud.

Tweaked vote-counting rules may delay official results by days, analysts say, raising tensions -- which some fear may boil over into violence.

RUSSIA TIES

A UNITA victory could weaken decades of close ties with Moscow, for whom the MPLA was a cold war proxy during Angola's 27-year civil war ending in 2002, while UNITA was U.S.-backed.

UNITA condemned "the invasion of Ukraine by Russia," Costa Junior said on Twitter. He also travelled to Brussels and Washington to build ties with Western partners before elections.

Russia's ambassador to Angola, Vladimir Tararov, was quoted in Angolan press in March as praising the country for its neutrality while lambasting UNITA for wanting to show it "stands with the West, the so-called civilised countries".

Lourenco has also opened up to the West since his election in 2017, but in March it abstained from supporting a United Nations resolution which condemned Russia's war in Ukraine.

"It is highly possible that a UNITA win would mean a distancing of Angola from Russia," Charles Ray, head of the Africa Programme at the Foreign Policy Research Institute, told Reuters, but only if it can consolidate power over a pro-Russian military first.

Lourenco has tried to improve relations with Washington, and just before the elections applied to join a trade agreement with the European Union and southern African states, which has been in force since 2016. Talks start in months.

Asked about this shift in stance, Costa Junior told Reuters over the weekend: "The image (Lourenco) built to the outside world is disappearing.".

Lourenco was "successful in terms of international relations", but that had not achieved positive consequences for Angolans, Ricardo Soares de Oliveira, professor of African Politics at Oxford University, said.

Lourenco has also pledged to continue economic reforms, including privatisation and encouraging the non-oil sector.