EU and Nato security personnel have been deployed to protect the builders
Disturbances have continued in the divided Kosovan town of Mitrovica, over the rebuilding of five houses owned by ethnic Albanians in a Serb district.
The Albanians were forced out of the northern, predominantly Serb part of the town, during fighting a decade ago.
Demonstrators opposed to their return have staged protests since last Friday, many of which have turned violent.
On Thursday evening, a European Union police convoy was attacked with petrol bombs and stones while on patrol.
No-one was injured in the incident, a spokesman for the force said.
Kosovo unilaterally declared its independence from Serbia in February 2008, something which Belgrade has refused to recognise.
The Serb minority and their religious sites are currently protected by a Nato-led force. Also helping to keep order is the EU's largest ever police and justice mission, Eulex, which deployed in December.
Despite the often violent protests from ethnic Serb residents of Mitrovica, building work continued on Friday on five homes that were destroyed in 1999, when Serbian security forces fought against ethnic Albanians who wanted independence for their province.
At one point, demonstrators broke through a security barricade, prompting members of Eulex to fire tear gas back at them.
The Serbs say they will end their protests if they are allowed by the international community and Kosovo's government to return to the predominantly Albanian southern part of Mitrovica.
On Thursday, the deputy head of the Eulex, Roy Reeve, told the BBC that its personnel, who were there to protect the builders, had been repeatedly attacked in recent days.
"During the course of this week, our policemen have had hand grenades thrown at them, exploding within 20 metres of their position. We have had shots fired in our direction as protesters have broken through Kosovo-Serb police lines and have moved towards the workers on the building site," he said.
"In response we've used tear gas and we've used a few stun grenades in order to deter them from coming closer. We're trying just to prevent them from getting in and interfering with legitimate work which is being undertaken."
But Mr Reeve said it was unsurprising that there had been opposition.
"For over a year there has been no rule of law in the north, there has been no effective policing, there's been no effective delivery of justice, the customs gates have been left empty," he said.
"I think any attempt to establish a system of rule of law in the north will be opposed," he added.