ISTANBUL — A vote to grant new powers to President Recep Tayyip Erdogan sparked fresh arguments in a divided Turkey on Monday, as opposition parties called for the annulment of the referendum results and Erdogan insisted the debate over the outcome should stop.
And a sharply worded report Monday by an international monitoring group said the referendum ‘‘fell short’’ of full adherence to international standards. It criticized numerous aspects of the vote, including a change to the ballot-counting procedures that ‘‘removed an important safeguard.’’
By a razor-thin margin, voters Sunday approved constitutional changes that will radically transform Turkey’s system of government, abolishing the post of prime minister and shifting from a parliamentary system to a strong president.
The new model increases the clout of the presidency just eight months after a coup attempt aimed at toppling Erdogan’s government.
The outcome has laid bare deep political divisions in Turkey and could have wider resonance in everything from Turkey’s decades-old bid for membership in the European Union and Turkish interactions within NATO to the US-led coalition fighting the Islamic State in neighboring Syria.
An unofficial tally carried by the country’s state-run news agency gave Erdogan’s ‘‘yes’’ vote a narrow win, with 51.4 percent approving 18 constitutional changes.
The referendum was held Sunday with a state of emergency still in place, imposed after the attempted coup in July.
On Monday, the country’s Council of Ministers decided to extend the state of emergency, which grants greater powers of detention and arrest to security forces, for a further three months. It had been due to expire April 19. Parliament must approve the extension.
Hopes that the end of the rancorous referendum campaign might suppress some of the country’s feuds seemed to evaporate late Sunday night.
As Erdogan’s supporters flooded streets in flag-waving celebrations, political opponents cried foul at the results and launched protests. Hundreds of ‘‘no’’ supporters demonstrated in Istanbul on Monday, chanting ‘‘thief, murderer, Erdogan.’’
In a combative speech at the presidential palace in Ankara on Monday evening, Erdogan dismissed the protesters as well as the opposition party complaints, saying that the ‘‘debate about this issue is now over.’’
And he warned the European observers who had criticized the election to ‘‘know your limits’’ as they prepared their final report, which he also dismissed, in advance.
The primary opposition complaint is that, as voting was underway, Turkey’s election board decided to accept thousands of ballots that were not stamped with an official seal. Election board officials have said they were trying to avoid suppressing votes and that the move was not unprecedented.
Bulent Tezcan, deputy leader of the Republican People’s Party, or CHP, Turkey’s main opposition party, said Monday that only one step could calm the nation — ‘‘for the referendum to be canceled by the Supreme Election Board.’’
Changes to the constitution would allow Erdogan, 63, who served as prime minister before becoming president, to run for reelection in 2019 and serve two terms, ending in 2029.
