United Nations envoy Martti Ahtisaari has urged Serbs in the divided Kosovo town of Mitrovica to join the province’s institutions and help in building a multi-ethnic society. Ahtisaari arrived in Pristina on Friday, just hours after police charged a demonstration held by ethnic Albanians outside the HQ of the United Nation’s Mission in Kosovo, calling for the departure of the multinational force and the cessation of negotiations with Belgrade over the future status of the province.The envoy, who heads UN mediated talks on the future status of Kosovo, made his comments after visiting Mitrovica, which has seen some of the worst post-war violence in the province, and has been divided between Serbs and ethnic Albanians since the 1998-99 war. Last week Serbs from northern Kosovo cut off ties with Pristina because of a spate of attacks which they blame on ethnic Albanians, who make up 90 per cent of the province’s population. The talks on Kosovo’s future started in February, in Vienna. Western diplomats have said they want a decision on the province’s final status within a year.