Police say Kosovo's parliament was hit with an explosive device late on August 4, causing damage to the building but no injuries.
Kosovo media reported that two motorcyclists fired a rocket-propelled grenade as they drove near the parliament building.
The downtown area was sealed off as police investigated.
The blast comes amid tensions over a border demarcation deal that the government has reached with Montenegro.
Earlier on August 4, the government ratified the deal and sent it to parliament. Lawmakers are expected to vote on it next week.
The deal sets the boundary between the two countries and is backed by the United States and European Union.
Adopting a the deal is a precondition for Kosovo to get a visa-free travel regime to the EU's Schengen zone as other countries in the region received in 2010, including Serbia, Albania, Montenegro, Macedonia, and Bosnia-Herzegovina.
Opposition parties and some members of the governing coalition are vehemently against the deal, however, saying it hands over 8,000 hectares of Kosovo land to Montenegro.
Since last year the opposition has used tear-gas canisters inside parliament and clashed with police outside in an attempt to scuttle the deal.