Croatia's President Zoran Milanović re-elected by a landslide in Sunday run-off

Croatia's opposition-backed President Zoran Milanović has scored a landslide win in Sunday’s second round presidential election, defeating a candidate from the ruling conservative party in a runoff vote, official results showed.

Milanović won more than 74% of the vote compared to his challenger Dragan Primorac, who received nearly 26%, according to the results released by Croatia's state election authorities after more than 99% of the ballots were counted.

The result presents a major boost for Milanović, who is a critic of Western military support for Ukraine in the war against Russia.

Milanović is also a fierce opponent of Croatia's conservative Prime Minister Andrej Plenković and his government.

In a speech after the results were released, Milanović said his victory was a sign of approval and trust from the voters but also presented a message "about the state of affairs in the country for those who need to hear it."

"I am asking them (the government) to hear it," said Milanović. "That is what the citizens wanted to say. This is not just support for me."

Milanović is the most popular politician in Croatia and is sometimes compared to US President-elect Donald Trump for his combative style of communication with political opponents.

Milanović also won comfortably in the first round of voting on 29 December, leaving Primorac, a forensic scientist who had unsuccessfully run for president previously, and six other candidates far behind.

The runoff between the top two contenders was necessary because Milanović fell short of securing 50% of the vote by just 5,000 votes, while Primorac trailed far behind with 19%.

The election was held as Croatia, which has a population of 3.8 million, struggles with biting inflation, corruption scandals and a labour shortage.

Casting his vote on Sunday, Milanović again criticised the EU as "in many ways non-democratic" and run by unelected officials.

The EU position that "if you don’t think the same as I do, then you're the enemy" amounts to "mental violence," Milanović said.

"That's not the modern Europe I want to live and work in," he said. "I will work on changing it, as much as I can as the president of a small nation."

His triumph sets the stage for a continued political confrontation with PM Plenković, with whom he sparred during his first term.

Milanović regularly accuses Plenković and his conservative HDZ of systemic corruption, while Plenković has labelled Milanović "pro-Russian" and a threat to Croatia's international standing.

Milanović denied he is pro-Russian but last year, he blocked the dispatch of five Croatian officers to NATO's mission in Germany called Security Assistance and Training for Ukraine.

He also pledged he would never approve sending Croatian soldiers as part of any NATO mission to Ukraine. Plenković and his government say there is no such proposal.

Despite limited powers, many believe the presidential position is key for the political balance of power in a country mainly governed by the Croatian Democratic Union, or HDZ, since gaining independence from Yugoslavia in 1991.

Meanwhile, contender Primorac entered politics in the early 2000s, when he was science and education minister in the HDZ-led government.

He unsuccessfully ran for the presidency in 2009, and after that mainly focused on his academic career including lecturing at universities in the United States, China and in Croatia.

"Zoran Milanović and me are separated by completely different spiritual, moral, professional values, as well as ideas about the future of our country," he told his supporters in Zagreb.

"The decision was made by citizens, democratically, and as such it must be respected."