SKOPJE, Macedonia -- Macedonia's president 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.

Police said 77 people, including opposition Social Democrat leader Zoran Zaev, the head of a small ethnic Albanian opposition party and 22 police, were injured in the overnight riot when demonstrators stormed the legislature and attacked lawmakers to protest the election of a new speaker despite a months-old deadlock in efforts to form a new government.

It was unclear whether opposition party leaders would heed President Gjorge Ivanov's call for a meeting to defuse the tension.

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The European Union condemned the violence, and said that the cornerstones of democracy should be respected.

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

Macedonia has been gripped by a deep political crisis for more than two years, and repeated efforts - including international mediation - have failed to improve things. The country has been without a government since elections in December failed to give any party a governing majority.

In response to tonight's events pic.twitter.com/jern5OI5GX — US Embassy Macedonia (@usembassymkd) April 27, 2017

The U.S. Embassy in Macedonia posted a message on its official Twitter account condemning the violence, saying it was "not consistent with democracy and is not an acceptable way to resolve differences."

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."