An unprecedented joint investigation by former foes Serbia and Bosnia culminated Friday in the arrests of 15 people suspected of kidnapping and murdering nearly two dozen Serbs in an attack during the 1992-1995 Bosnian War, officials said.

The arrests over the 1993 attack on a train transporting Serbs along the border with Bosnia took place in coordinated raids in both jurisdictions.

Croatian Prime Minister Zoran Milanovic on Friday canceled a planned trip to Serbia next month amid growing tensions between the former foes sparked by the release of Serb war crimes suspect Vojislav Seselj on health grounds.

Milanovic decided not to attend a December 16 meeting in Belgrade of his central and eastern European counterparts along with Chinese Prime Minister Li Keqiang, citing the Serbian authorities' lack of action in response to inflammatory statements from Seselj, a government spokesman told AFP.

The European parliament on Thursday urged Belgrade, a candidate for EU membership, to crack down on Serb ultra-nationalist Vojislav Seselj who was released by a U.N. war crimes court for cancer treatment.

In a resolution adopted in the French city of Strasbourg, the parliament said it deplores Seselj's "provocative public activities and wartime rhetoric since his provisional release" two weeks ago.

Serbian nationalist firebrand Vojislav Seselj is spearheading an anti-government rally on Saturday but as he fights cancer and awaits judgment on war crimes charges he is as beleaguered as his once formidable party.

His fit appearance and jovial manner during a rapturous homecoming welcome on Wednesday belied the fact that he was back in Serbia because a U.N. tribunal in The Hague decided he is so sick that it ordered him to return home for cancer treatment immediately.

Serb ultranationalist leader Vojislav Seselj made a fiery return home on Wednesday following his release by a UN war crimes tribunal for cancer treatment, branding his country's leaders "traitors".

Welcomed at the airport by family, officials from his party and more than 1,000 supporters, the defiant hardliner -- who is charged with war crimes and crimes against humanity -- vowed to chase from power his former allies.

An historic fence-building visit to Belgrade by Albanian Prime Minister Edi Rama took a disastrous turn Monday when the leaders of the two countries clashed publicly over Kosovo.

All was going well as Rama and Serbian Prime Minister Aleksandar Vucic spoke to reporters about turning the page on stormy relations between the two Balkan neighbors until the Albanian mentioned Kosovo, calling on Serbia to recognize the "irreversible reality" of its independence.

Albanian Prime Minister Edi Rama will make a landmark visit to Belgrade on Monday, the first of its kind in 68 years and seen as a step towards calming tensions in the region.

Initially planned for October 22, the visit was postponed for three weeks following violence a week earlier that interrupted a football match between Serbia and Albania.

Just when Kosovo appeared to be heading for a degree of stability and normalcy, feuding politicians and fresh corruption scandals have plunged the fledgling Balkan nation into its worst political crisis to date.

A quirk in the young nation's constitution has left Kosovo in a seemingly unfixable political deadlock that could yet force fresh elections only five months after the last vote.

Kosovo's foreign minister made a landmark visit to Serbia on Thursday, the first since the former Serbian province unilaterally declared independence in 2008 to the fury of Belgrade.

The presence of Enver Hoxhaj and his Albanian counterpart Ditmir Bushati in the Serbian capital was seen as a sign that a recent flare-up of tensions between Serbs and ethnic Albanians is calming.

Albania on Sunday condemned the burning of its flag during a football match in Serbia, the latest in a series of incidents aggravating political tensions between Belgrade and Tirana.

The Albanian foreign ministry urged Serbian authorities to bring the preparators to justice and called on "Serbian politicians to distance themselves from those acts that are... harmful for the future and stability of the Balkans."