ANKARA, Turkey (AP) — Turkey’s prime minister has called on the opposition to respect the result of a referendum that will expand the powers of the office of the president.

In an address to legislators from his ruling party on Tuesday, Binali Yildirim said the people had voted to switch from a parliamentary to a presidential system, adding: the “opposition should not speak after the people have spoken.”

An unofficial tally carried by the country’s state-run news agency gave President Recep Tayyip Erdogan’s “yes” camp a narrow win.

Opposition parties called for the vote to be annulled because of a series of irregularities, particularly an electoral board decision to accept ballots that didn’t bear official stamps, as required by Turkish law.

International monitors said the move undermined safeguards against fraud.