ZAGREB, Croatia (AP) — Croatia's ruling center-left coalition faces a strong challenge from a conservative opposition in the Balkan country's first parliamentary election since joining the European Union in 2013.

Neither the conservatives, led by former intelligence chief Tomislav Karamarko, nor the center-left coalition, led by incumbent Prime Minister Zoran Milanovic, are expected to win an outright majority in Sunday's vote. The forming of the new government will depend on several small parties that are expected to enter the 151-seat parliament.

The outcome of the vote could disrupt the flow of migrants crossing the small country if the conservatives return to power and carry out pledges to implement tough measures against the surge. Since September, Croatia has seen an influx of over 300,000 people fleeing war and poverty and seeking a better life in wealthier EU states such as Germany.

The conservatives have criticized Milanovic's government for allowing the free flow of migrants and have hinted they would build fences and deploy the army to the border to stop the flow.

Croatia, with a population of 4.2 million, has one of EU's worst economies. It only recently emerged from a six-year recession but unemployment is hovering around 16 percent, of which 43 percent are young people.

Sunday's vote is likely to represent a revival for Karamarko's conservative Croatian Democratic Union party, which led Croatia during its war for independence from the Serb-led Yugoslavia in the 1990s and then dominated its political scene for years. Its popularity plummeted after a series of corruption trials against top officials.

The presidential election victory earlier this year of a conservative, Kolinda Grabar-Kitarevic, was a clear sign that Croatia is shifting to the right after a four-year rule of the center-left bloc.

Karamarko campaigned on patriotism and creating new jobs, while Milanovic promised economic revival and warned against allowing Croatia to return to its conservative past.