A Turkish court on Sunday jailed the mayor of Istanbul pending his trial on corruption charges, according to the state-run Anadolu news agency, hobbling a potential contender in Turkey’s next presidential election and the top rival of President Recep Tayyip Erdogan.

The mayor, Ekrem Imamoglu, was arrested at his home on Wednesday, four days before he was set to be named the presidential candidate of Turkey’s political opposition. He has denied the accusations against him, which Mr. Erdogan’s opponents have called a ploy to hinder a popular politician’s presidential bid.

The court ordered that Mr. Imamoglu be jailed on accusations of corruption pending a trial, the state-run news media said. State prosecutors have accused him of leading a criminal organization and overseeing bribery, bid rigging and other financial misdeeds at City Hall.

Prosecutors also accused him of supporting terrorism through his political coordination with a pro-Kurdish group during local elections last year. The court has not yet ruled on whether he will be jailed for those accusations as well.

The decision to jail Mr. Imamoglu, who has been elected mayor three times since 2019, raised the possibility that he would be removed from office.

That alone may not prevent him from running for president, but he faces other roadblocks. The day before his arrest, his alma mater, Istanbul University, voided his diploma, citing improper procedures in his transfer to the school in 1990. Turkey’s Constitution stipulates that the president must have completed higher education. The mayor said before he was detained that he would contest the ruling.

Mr. Imamoglu faces a slew of other court cases as well, including some that could temporarily bar him from politics.

In a post on X, the mayor called on Turks to stand together against “this black stain on our democracy,”

Of his detention, he said: “I stand tall. I will never bow.”

Critics of Mr. Erdogan, who has dominated Turkish politics for more than two decades, have long accused him of using state power to undermine his rivals. But, they say, arresting a presidential contender to eliminate him from the race before it begins represents a new level of authoritarianism.

Some European leaders have criticized the mayor’s arrest, which has prompted protests around Turkey, and they have called on the Turkish government to uphold the rule of law. Senior U.S. officials have said little.

Steve Witkoff, President Trump’s Middle East envoy, made no mention of the mayor’s detention in an interview with the former Fox News anchor Tucker Carlson that was posted on X on Saturday. But he said that Mr. Trump had recently spoken with Mr. Erdogan. The call was not made public by the White House at the time.

“There is just a lot of good, positive news coming out of Turkey right now as a result of that conversation,” Mr. Witkoff said, without providing further details.

Despite Mr. Imamoglu’s detention, Turkey’s main opposition party, the Republican People’s Party, or C.H.P., has gone ahead with a primary on Sunday to formally designate him its presidential candidate. Party members voted around the country, and the party called on nonparty members to turn out as well to cast symbolic ballots to support the jailed mayor.

Mr. Erdogan’s current presidential term, his second, expires in 2028. While the Constitution limits presidents to two full terms, he could legally run again if Parliament called for early elections, cutting short his second mandate.

Many people in Turkey expect that to happen. If it does, it is possible that Mr. Imamoglu, 54, could be barred from the race. Mr. Erdogan, 71, has not said whether he would run, but he has no clear successor and many people in Turkey expect him to seek another term.

The jailing of Mr. Imamoglu could disrupt the administration of Turkey’s largest city. The city government employs more than 100,000 people and oversees a number of companies that build housing, run public transportation and carry out infrastructure projects.

Large protests against Mr. Imamoglu’s detention have broken out nightly in cities across Turkey, despite the government’s efforts to stop them. Public demonstrations have been banned in the country’s three largest cities, social medial access has been restricted and major transit hubs have been closed to hamper the ability of protesters to gather in public squares.

On Saturday, the Interior Ministry said that 343 people had been arrested while protesting, and the office of Istanbul’s governor, who is appointed by Mr. Erdogan, said travelers “likely to participate in unlawful protests” would be prevented from entering the city.

Safak Timur and Gulsin Harman contributed reporting.