PRISTINA (AFP) - Kosovo and EU police and customs officers took control on Friday of two disputed border crossings with Serbia in a move that raised fears of a fresh wave of ethnic violence in a tense Balkan region. They were deployed with the assistance of NATO peacekeepers KFOR in the latest move by Pristina to assert control over northern Kosovo, populated by a large ethnic Serb minority which rejects Kosovo's declaration of independence from Serbia in 2008. Kosovo prime minister Hashim Thaci said the "process has successfully began ... and Kosovo police and customs officials, together with (EU rule of law mission) EULEX and KFOR are now at the two border crossings." "I appeal to all citizens for peace and restraint," Thaci told reporters after a session of his ethnic Albanian majority cabinet in Pristina. "I called on Belgrade to finally give up (its) disappointing attempt to destabilise the region and once and for all accept that Kosovo is independent, one and indivisible," Thaci said. In Vienna, pan-European security body OSCE urged "calm and restraint" and called all parties to "act responsibly". "Outstanding issues should be resolved in a calm and responsible manner through the EU-led dialogue," Lithuanian Foreign Minister Audronius Azubalis, current chairman of the Vienna-based Organisation for Security and Co-operation in Europe (OSCE), said in a statement.