Kosovo's Constitutional Court has approved a contested government deal on giving more powers to ethnic Serbs in Kosovo.

In its ruling Wednesday, the court also asked the government to complete some legal aspects of the deal, saying some of its principles are not in line with the constitution.

The deal on Serb minority rights, and another one on border demarcation with Montenegro have sparked ferocious protests by the opposition which has tried to block work in Kosovo's Parliament with tear gas, pepper spray, whistles and water bottles.

The opposition has called for a referendum or fresh elections if the government doesn't halt the deals and opposition supporters have held violent protests in Pristina.

Kosovo declared independence from Serbia in 2008, an act that Serbia still rejects.