Thirteen people were injured Saturday, including two seriously, when a local train hit a bus at a level crossing in southern Croatia, police said.

The accident occurred near the southern town of Drnis, some 220 kilometers (135 miles) southeast of Zagreb, a police spokeswoman said.

Twelve Croatian lawmakers officially took their seats in the European Parliament in Strasbourg on Monday, after their country became the European Union's 28th member state.

"This a special day in the history of the EU and of Croatia," European Parliament president Martin Schulz said as he received the new members who were elected in April.

Croatia woke up on Monday as the newest EU state after a night of celebrations dampened by fears that membership to the bloc could add to the recession-hit country's economic burden.

"Good morning, citizens of the European Union," popular daily Jutarnji List wrote on its front page.

Tens of thousands of Croatians cheered the country's entry into the European Union at midnight Sunday as fireworks lit up the skies above Zagreb.

It was a historic moment for the former Yugoslav republic, coming nearly two decades after it emerged from a bloody independence war in the 1990s.

Former Bosnian Croat President Jadranko Prlic and five co-accused were on Wednesday jailed for between 25 and 10 years for murdering and deporting Muslims in Bosnia in the early 1990s to create a "greater Croatian state."

The six, all top former Bosnian Croat officials, faced 26 counts of war crimes and crimes against humanity for their roles in the brutal conflict which formed part of the greater war that broke out after Yugoslavia crumbled in 1991 and in which 100,000 people were killed.

Forget the European Union, many in this Croatian village are saying. The group of nations being celebrated this weekend is one that died more than 20 years ago when Yugoslavia — now fervently remembered as a haven of peace, prosperity and equality — fell apart in a cascade of ethnic wars.

Thousands of people came together Saturday in the birthplace of Yugoslavia's late communist leader, Josip Broz Tito, to mark his birthday and pay their respects to him and the ex-federation.

Croatians cast ballots on Sunday for municipal officials in a vote seen as a test for the center-left government and its austerity policies, six weeks ahead of the former Yugoslav republic's EU entry.

The latest surveys showed that the popularity of Prime Minister Zoran Milanovic's government, led by his Social Democrats (SDP), has hit the lowest point since it won late 2011 elections.

Some 20,000 Muslims from Croatia and abroad gathered in the Adriatic port city of Rijeka on Saturday to inaugurate an Islamic center and the third mosque in the staunchly Catholic country.

"Multiculturalism and diversity are among basic values on which the European Union is built," the head of EU delegation here, Paul Vandoren, said, a reminder that Croatia was set to join the bloc on July 1.

The top leader of one of Bosnia's two semi-autonomous entities, the Muslim-Croat federation, and 18 other people were arrested on Friday in a wide anti-corruption probe, judicial sources said.

Zivko Budimir, Bosnian Croat president of the Muslim-Croat federation which together with Serb-run Republika Srpska make up post-war Bosnia, was arrested in the action, prosecutor's spokesman Boris Grubesic said.

Arab nations and Turkey, helped by the CIA, have dramatically increased military aid to Syrian rebels in recent months, The New York Times reported Monday.

The U.S. Central Intelligence Agency was helping their efforts, the newspaper added, citing air traffic data and interviews with unnamed officials and the rebel commanders.