PRISTINA, Kosovo — A Kosovo opposition lawmaker and three other supporters were convicted Friday of terror charges and sentenced to prison over a rocket-propelled grenade attack on parliament.

The Pristina court sentenced Frasher Krasniqi, lawmaker of the Self-Determination Movement party, to eight years.

The three others were imprisoned to between two and six years for the Aug. 4, 2016 attack that damaged the building’s exterior but caused no casualties. Adea Batusha, who was sentenced to two years in jail, was released since she had already served her term in pre-trial detention.

The court verdict said that the defendants, “acting as a group with special roles since July 2016, had prepared and planned preparatory acts to commit the penal act of attacking the parliament building.”

Defense lawyer Tom Gashi said that his clients will appeal the verdict, adding they were jailed without any evidence. Astrit Dehari, another supporter arrested at the time, died in prison after a few months in still unclear circumstances.

The Self-Determination Party leader Visar Ymeri considered the verdict as “political” as the “judge based his verdict on political orders, without any evidence … to damage (the party) two days ahead of the municipal election runoffs on Sunday.”

The attack occurred amid political tensions over the government’s agreement with neighboring Montenegro determining their common border.

Opposition parties vehemently oppose the deal, arguing it cedes territory to Montenegro, which wasn’t accepted by the previous government or international experts.

Approval of the deal is a pre-condition for a visa-free regime for Kosovo citizens in the European Union’s Schengen countries. That deal still remains an unresolved challenge for the new government in power since September.

The opposition is also against another agreement giving more powers to ethnic Serbs in Kosovo.

Opposition lawmakers have disrupted parliamentary work in recent times by using tear gas canisters, blowing whistles and throwing water bottles. Outside parliament, street rallies by opposition supporters routinely turned into violent clashes with police.