PRISTINA (Reuters) – Protesting Serbs in the ethnically divided city of Mitrovica in northern Kosovo erected new barricades on Tuesday, hours after Serbia said it had put its army on the highest combat alert following weeks of escalating tensions between Belgrade and Pristina. Serbia’s defence ministry said that given the latest events in the region and Belgrade’s belief that Kosovo was preparing to attack Serbs and forcefully remove the barricades, President Aleksandar Vucic had ordered Serbia’s army and police to be put on the highest alert. Kosovo’s government called on NATO peacekeepers to…