BUDAPEST/BELGRADE (BLOOMBERG) - The two European leaders most closely allied to Russian President Vladimir Putin before he launched his invasion of Ukraine won decisive election victories on pledges to stay out of the war.

Hungarian Prime Minister Viktor Orban, who has spent 12 years consolidating his grip on power and clashing with the European Union over democratic values, clinched a fourth consecutive term in a crushing victory over a broad opposition alliance.

In neighbouring Serbia, Mr Aleksandar Vucic won five more years as president and his ruling Serbian Progressive Party was in position to form a majority-backed government. Like Mr Orban, he has drawn criticism from his rivals and countries in the EU, which he wants Serbia to join, for suppressing political opposition.

Both had until recently defied warnings from western partners by cultivating ties with Moscow and Beijing.

Mr Putin was among the world's first leaders to congratulate Mr Orban and Mr Vucic on their victories.

The results expose one of the thorniest issues facing the EU: How to deal with current members or future aspirants who defy the bloc's rule-of-law standards and veer from peers on important geopolitical issues such as Ukraine.

At the same time, Mr Orban and Mr Vucic may face deeper international isolation, with Hungary at risk of losing billions of euros in EU funding and Serbia struggling to advance with talks to join the wealthy single market.

Mr Orban's party maintained its two-thirds majority in the 199-seat parliament, according to results with more than 99 per cent of ballots counted. A majority of that size will allow it to change any law, including the constitution, without opposition support. It may also embolden the premier in his battles with the Brussels-based EU.

"Brussels should brace itself for new troubles, because everything that it found loathsome in Hungary's maverick PM previously will now certainly be intensified for at least the next few months - but in all likelihood, for the next four years," said Mr Mujtaba Rahman, a managing director for the Eurasia Group political risk consultancy.

The war in Hungary's eastern neighbour, which has killed thousands of civilians and driven more than 4 million to flee abroad, upended the election campaign, forcing 58-year-old Mr Orban to walk a political tightrope.

He tried to distance himself from Mr Putin by condemning Russia's actions and backing EU sanctions against his regime, while opening Hungary's borders to about half a million Ukrainian refugees.

Still, Mr Orban limited support for Kyiv, refusing to let weapons shipments cross Hungary and rejecting a ban of Russian oil and gas imports, drawing condemnation from Ukrainian President Volodymyr Zelensky.

"He is virtually the only one in Europe to openly support Mr Putin," Mr Zelensky said a day before Hungary's vote, referring to Mr Orban.

The Hungarian leader's nationalist message - heavily supported by pro-government media outlets that he has transformed into a propaganda machine - was that joining a rush by fellow EU and Nato members to aid Ukraine with weapons would drag Hungary into the war. That resonated with voters, while the opposition suggested that the ballot was a choice between East and West.

"We scored such a huge victory that was visible even from the Moon, but certainly from Brussels," Mr Orban told supporters after the vote, referring to the seat of the EU in the Belgian capital.

Hitting back at Mr Zelensky, he listed the Ukrainian leader as having joined an "overwhelming force" of opponents who tried to stop him from winning a new term.

Mr Orban may have little time to celebrate. He'll have to navigate a new EU mechanism that links funding to adherence to rule of law, which was adopted after the Hungarian premier outmaneuvered the bloc's concerns about the rollback of democratic norms for the better part of the decade.

Should it be activated this year, it threatens to deprive Hungary of as much as US$40 billion (S$54 billion). Unlike before, Mr Orban may no longer be able to count even on his closest EU allies. His most outspoken critics, in fact, have been Hungary's regional peers including Poland, whose president warned Mr Orban that his policy toward Ukraine would end up being "very costly" for him.

Putin ally

Mr Vucic, 52, secured 59 per cent of the vote in the presidential contest, more than enough to avoid a runoff, according to official returns with 95 per cent of votes counted. His Progressive Party-led bloc won about 43 per cent in the parliamentary ballot.

He has struck a balanced position between Russia, a traditional Serbian ally, and the EU, which has piled pressure on Belgrade to adopt its raft of sanctions targeting the Kremlin.

Although Serbia condemned Mr Putin's invasion of Ukraine in a United Nations resolution, Mr Vucic has said it's not in the country's interest to join the EU penalties.

The opposition has failed to gain traction in a country with divided sympathies between Moscow and the EU.

A poll last month showed that half of Serbs want their country to remain neutral, though of those to choose a side, more expressed a preference for Russia.

"The most important thing for Serbia is to have good relations in the region and to continue on its European path, without ruining its ties with traditional friends," Mr Vucic told supporters late on Sunday.