WARSAW — Macedonia’s main opposition leader has been formally indicted on charges of wiretapping and antigovernment activities after months of political turmoil, prosecutors said this week.

The leader of the left-wing Social Democratic Union of Macedonia, Zoran Zaev, was charged with “one continuous criminal act of unauthorized wiretapping and audio recording” as well as “violence against representatives of the highest authorities,” according to a statement posted on the state prosecutor’s website late Thursday.

The indictment came shortly after Mr. Zaev unveiled plans for a mass protest in the capital of the landlocked Balkan nation, Skopje, to be held this month — “the biggest one that the country has seen,” he said.

Macedonian politics have been rocked for months by Mr. Zaev’s release, bit by bit, of leaked transcripts of what he said were thousands of government-made recordings of conversations involving government officials and others. Mr. Zaev says they point to instances of corruption, vote-rigging and manipulation of the criminal justice system.