An explosive device was fired at Kosovo's Parliament, causing damage to the building but no injuries.
The central area of Pristina was sealed off as the authorities began their investigation, with police saying that the device was fired from a distance.
The blast comes amid tensions over a border demarcation deal that the government has reached with Montenegro.
Earlier on Thursday, the government ratified the deal and sent it to Parliament. Politicians are expected to vote on it next week.
The deal sets the boundary between the two countries and is backed by the US and EU.
The opposition parties and even some members of the governing coalition are vehemently against the deal, saying it hands over land to Montenegro.
Since last year the opposition has used tear gas canisters inside Parliament and clashed with police outside in an attempt to scupper the deal.