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BELGRADE, April 24 (Xinhua) -- Serbian citizens started casting their ballots in Sunday's snap parliamentary elections seen by many as a test to the Balkan country's efforts to join the European Union (EU).

Serbian Prime Minister Aleksandar Vucic votes at a polling station in Belgrade, Serbia on April 24, 2016. Serbian citizens started casting their ballots in Sunday's snap parliamentary elections seen by many as a test to the Balkan country's efforts to join the European Union (EU). (Xinhua/Predrag Milosavljevic)

The elections, called by Prime Minister Aleksandar Vucic two years before his term ends, are expected to give him another full four-year mandate for reforms to pave the way for Serbia's full membership in the European Union.

Vucic said that by voting in fresh elections, people will decide "whether Serbia will become a modern European country by 2020."

According to the electoral officials, voting will take place at around 8,500 polling stations, while around 56 percent of the 6.7 million eligible voters will cast their ballots.

Preliminary results are probably due late Sunday night. The prime minister's ruling Progressive Party (SNS) is expected to win about half of the votes, enough to grant the SNS a majority in the 250-seat National Assembly, according to a latest research performed by the Center for Free Elections and Democracy (CESID).

However, the elections are also likely to bring the pro-Russian far-right back to the parliament, according to the research.

Serbia started its formal accession negotiations with the EU in December. Brussels has said there will be no further enlargement until 2020.

Local media reports said that the elections will be monitored by 1,687 domestic and 196 foreign observers.