Bosnia's autonomous Serb region said on Thursday it would halt cooperation with the national court, prosecutor and police in protest at a war crimes raid, further threatening the integrity of the country 20 years after it emerged from war.
The step was announced by the Serb Republic government but required the approval of the local parliament, which was sitting in emergency session.
Bosnian Serb leader Milorad Dodik is already threatening to hold a referendum on the jurisdiction of Bosnia's national court, deepening concern in the West that the two autonomous components of the fragile state created at the end of the war could break apart.
The Serb government acted after a raid by the national SIPA police on a local police station and municipal buildings in the Serb Republic as part of an investigation into war crimes committed during Bosnia's 1992-95 war.
Five Serbs were arrested during the operation on suspicion of involvement in the murder of 27 Muslim Bosniaks in the area.
Decrying the raid as "inappropriate and provocative," the Serb government said it and all institutions of the Serb Republic were "breaking off cooperation with the Bosnian court, Bosnian prosecution and SIPA."
It accused the Bosnian national court of demonstrating a lack of trust in the regional police by not giving advance warning of the operation out of fear that evidence might be destroyed.
The government ordered the Serb Interior Ministry to "prevent any entry or search of (Serb) Republic and local government premises."
The state prosecutor's office said the raids had been ordered on the basis of evidence that "police and civil defence structures in Novi Grad actively and directly" took part in the removal and concealment of 27 victims of the war.
"The raids were conducted exclusively to search for archive materials and evidence in these illegal acts," it said.
An estimated 100,000 people died in Bosnia's 1992-95 war as federal Yugoslavia broke apart.
A peace accord split the country into two autonomous regions joined by a weak central government in an unwieldy system of ethnic quotas that critics say has stunted development and further entrenched ethnic nationalism.