The president of Macedonia has made an appeal to the nation for calm, after scores of protesters, many wearing masks, stormed the country's parliament late on Thursday night.
Shouting and throwing chairs, they attacked lawmakers in protest at the election of an Albanian parliament speaker despite the country's long stalemate in the formation of a new government.
President Gjorge Ivanov said in a televised address that the election had "violated" the constitution, but nonetheless called appealed for "for reasonable and responsible behaviour".
Police used flash grenades in clashes with protesters outside the parliament building after the assault.
Authorities say 77 people have been injured in the clashes inside and outside parliament.
The injured included 22 police officers and three lawmakers who were attacked when dozens of protesters pushed through a police cordon and stormed into parliament.
Television footage showed Zoran Zaev, the Social Democratic leader, and other members of the party being attacked by protesters waving national flags, shouting "traitors" and refusing to allow them to leave. The images showed blood trickling from one side of Mr Zaev's forehead.
Elections were held in December 2016 and won by former prime minister Nikola Gruevski's conservative party, but without enough votes to form a government.
Mr Zaev has been seeking a mandate to form a government for months, after reaching an agreement with an ethnic Albanian party, the Democratic Union for Integration, to form a coalition government. However, Mr Ivanov, the president, has refused to hand him the mandate.
European Union officials had called on the president to respect the election result and to allow the Social Democrats to form a government.
The US embassy in Macedonia has condemned the violence in the country's parliament, after scores of protesters stormed the building and attacked lawmakers.
In response to tonight's events pic.twitter.com/jern5OI5GX— US Embassy Macedonia (@usembassymkd) 27 April 2017
The embassy said in a statement that the assault "is not consistent with democracy and is not an acceptable way to resolve differences."
Pressure had also been rising on the Democrats to force a breakthrough despite growing talk of a possibly violent reaction from their opponents.
The Assembly of the Republic of Macedonia, as the Balkan nation's parliament is known, has been deadlocked for three weeks over electing a new speaker.
Mr Zaev had suggested earlier on Thursday that one could be elected outside normal procedures, prompting widespread anger among opponents.
Also earlier on Thursday rumours of possible coup had swirled around Macedonia, and although denied they added to more heat to the already simmering political atmosphere.
Mr Zaev went ahead with the vote, and a majority in parliament elected Talat Xhaferi, a former defence minister and member of the Democratic Union for Integration.
The protesters who stormed parliament on Thursday night were among a group of demonstrators who have been holding protest rallies nightly for the past two months in the streets of Skopje and other cities in the country over the political situation.
European Union Enlargement Commissioner Johannes Hahn condemned Thursday's violence.
And the US embassy in Macedonia said in a statement that the assault "is not consistent with democracy and is not an acceptable way to resolve differences."
Greece's Foreign Ministry says it is concerned that neighboring Macedonia may be "sliding into deep political crisis."
A ministry statement issued late Thursday expresses "sadness and concern" at the assault on parliament and calls on Macedonia's political rivals to show a "spirit of compromise and collaboration."
Without it, the ministry says, "impasses can lead to explosive situations."