The leader of Macedonia's opposition has been charged with preparing a coup and prevented from leaving the country.

Zoran Zaev, leader of the Social Democratic Union party, has been charged with "violence against representatives of the highest state authorities." He was questioned by an investigative judge, but wasn't arrested and was ordered to hand over his passport, local media reported.

Prime Minister Nikola Gruevski accused Zaev Saturday of trying to blackmail him into resigning and giving way to a government of technicians by threatening to publish compromising phone conversations.

Last weekend, authorities arrested former intelligence chief Zoran Verusevski, his wife and one other man, in connection with the case.

Zaev's party has been boycotting parliament, accusing the ruling conservatives of fraud in the April 2014 election.