Turkey’s parliament has voted to close private preparatory schools, many of which are a source of income and influence for an Islamic cleric accused by Prime Minister Recep Tayyip Erdogan of covertly seeking to topple him.

Lawmakers on Friday set a deadline of Sept. 1, 2015, for the closures, news channels reported. Millions of students prepare at the centers for entrance examinations to win limited spots at state high schools and universities.

Erdogan has accused cleric Fethullah Gulen, a former Erdogan ally whose followers wield influence in the police and judiciary, of concocting a graft scandal to compromise his government. The scandal broke with police raids on Dec. 17; relations between the men have been tense in recent years.

“Pull your kids out, if they go to these schools. State schools are enough,” Erdogan said Saturday at a campaign rally in the western town of Denizli ahead of local elections set for March 30. “They have sucked like leeches. Leeches are more virtuous: Leeches suck dirty blood, while they suck clean blood and hold sessions cursing me, my wife, my children, my administration.”

Followers of Gulen, who preaches respect for science, democracy and dialogue with other faiths, have forged a powerful ­socio-religious community network. However, Gulen, who lives in self-imposed exile in Pennsylvania, says he has no plans to form a political party and denies any involvement in the graft investigation.

The government moved to shut down the exam preparation centers in November, worsening the public row with Gulen’s supporters.

This month’s election is seen as a critical test of support for Erdogan after 11 years in power.

Last week, audio recordings purportedly of Erdogan and his son Bilal discussing moving large sums of money and accepting bribes were posted on the Internet. Erdogan has said the audio was manipulated, and on Saturday he suggested that Gulen was behind the “conspiracy.”

“Listening to my phone is forbidden. They listened to me, the president, my family,” Erdogan said at the rally. “Now they’ve been caught. We are going into their lairs. It will take time, but we will begin a new era with the votes we win on March 30.”

Police used tear gas Saturday to disperse anti-government protests in Istanbul and the capital, Ankara. Such demonstrations have become frequent in city centers in the past few weeks.