Macedonian President Gjorge Ivanov called an emergency meeting of political leaders Friday, hours after demonstrators, mostly supporters of the country's dominant conservative party, invaded parliament and assaulted opposition lawmakers, the Associated Press reported.

But it was unclear whether opposition leaders would attend, and political tension remained high after the riot in which 77 people were injured, mostly lightly. Victims included opposition Social Democrat leader Zoran Zaev, the head of a small ethnic Albanian opposition party and 22 police.

The European Union condemned Thursday's violence, and said that the cornerstones of democracy should be respected. In neighboring Serbia, Prime Minister Aleksandar Vucic called emergency security consultations over the unrest.

Conservative VMRO-DPMNE leader Nikola Gruevski also deplored the violence, but said his political opponents provoked it.

Speaking at his party headquarters early Friday, Gruevski said the Social Democrats consciously broke the country's law and constitution by electing a new parliament speaker — an ethnic Albanian politician — despite the months-old deadlock in efforts to form a new government.

"Greed to seize power at any cost is the direct cause which led to this adverse situation, and they bear responsibility for it," Gruevski said.

The violence started when dozens of protesters, many masked, broke through a police cordon after the speaker's election, shouting, throwing chairs and wielding camera tripods abandoned by startled journalists.

Police said arrests have been made, but gave no further details.

Clashes lasted for hours Thursday night, with police initially doing little to stop the invasion, and the crowd inside parliament swelled to several hundred. Eventually, police used stun grenades to evacuate the building, and free lawmakers and journalists trapped inside.

EU foreign affairs chief Federica Mogherini said Friday that "violence is unacceptable, even more so when it happens in the house of democracy."

Mogherini, attending a meeting of EU foreign ministers in Malta, called the incident a "serious crisis that can be dangerous."

Macedonia's political crisis started in early 2015, when Zaev accused then-prime minister Gruevski of masterminding a massive illegal wiretapping operation against the judiciary, police, politicians, journalists, foreign diplomats and religious leaders.

Gruevski denies wrongdoing, and has blamed the wiretaps on unspecified foreign spies.