Former Kosovo prime minister Ramush Haradinaj, acquitted by a U.N. court of war crimes during the 1990s Kosovo conflict, said he was detained Wednesday at Ljubljana airport on an Interpol warrant issued by Serbia.

"I was in transit, the checking of my documents was lasting for a long time and when I asked what was going on ... I was told that there was an arrest warrant that was still valid," Haradinaj told AFP over the phone.

Some 1,000 Kosovo Albanians, mostly veterans of the 1990s war with Serbia, protested Wednesday against the creation of a special court that would handle war crimes allegedly committed by former ethnic Albanian guerrillas.

"History shows that there are no crimes when a nation fights for freedom," Xhavit Jashari, a veteran leader, told the protesters who gathered in front of the government and parliament buildings in the capital Pristina.

Hungary's foreign minister said Wednesday the government has ordered the closure of the EU country's border with Serbia and the construction of a fence along its length to keep out migrants.

"The Hungarian government has instructed the interior ministry to physically close the border with Serbia," Peter Szijjarto told reporters.

Serbian President Tomislav Nikolic Monday called off a visit to Bosnia after a member of Bosnia's tripartite presidency opposed his trip over the arrest of a former Bosnian Muslim fighter on Serbian war crimes charges.

Nikolic had been set to arrive in Sarajevo on Tuesday, on his first official visit since 2012.

Serbian investigators arrested 29 police officers and nine customs officials suspected of corruption, abuse of power and taking bribes, the interior ministry said Monday.

Those arrested are suspected of allowing trafficking of goods in exchange for bribes for more than a year around the northern town of Sombor, the ministry added in a statement.

Several hundred Muslim veterans of Bosnia's 1990s wars attended a protest Friday to demand the release of Naser Oric, a Bosnian Muslim commander arrested on a Serbian warrant alleging war crimes.

"We did not come to defend Naser Oric, because we know he is innocent," said one of the veterans, Zulfo Salihovic at a protest in Bosnia's capital Sarajevo.

EU member Hungary threatened Friday to close its border with Serbia to stop an influx of migrants.

"We don't think it's right that they send us the refugees, they need to be stopped on Serbian territory," Hungary's Prime Minister Viktor Orban said in an interview on Kossuth public radio.

Families of the thousands of Bosnian Muslims massacred at Srebrenica reacted with outrage Thursday over the arrest of former Bosnian Muslim commander Naser Oric on a war crimes warrant from Serbia.

Oric led the Bosnian Muslim forces in Srebrenica in eastern Bosnia, where Bosnian Serb forces slaughtered almost 8,000 Bosnian Muslim men and boys in mid-July 1995. 

Serbian Prime Minister Aleksandar Vucic arrived in Albania on Wednesday for the first such visit by a Serbian head of government as the two Balkan countries seek to improve fragile ties.

Vucic was greeted on arrival by his Albanian counterpart Edi Rama, who visited Belgrade six months ago in the first visit by a Tirana head of government for 68 years.

Serbia's justice ministry on Tuesday said it had received an order from a U.N. war crimes court to return the ailing ultra-nationalist Vojislav Seselj immediately to its detention unit.

Alleged war criminal Seselj, 60, was allowed to travel to Serbia last year for cancer treatment pending a verdict in his case at the International Criminal Tribunal for the former Yugoslavia (ICTY) in The Hague, and he underwent emergency surgery earlier this month.