ISTANBUL — President Recep Tayyip Erdogan of Turkey appeared to faint on Sunday because of what he said were complications with his blood-sugar level and blood pressure.

Mr. Erdogan, 63, was sitting for early morning prayers when he seemed to lose consciousness for a few moments at a mosque in Istanbul, several Turkish news outlets reported. He was quickly treated on a stretcher by doctors and made a rapid recovery; less than an hour later, he gave an explanation for the incident in a speech to reporters.

“Today, I had a little instability due to my blood pressure, for reasons related to my blood sugar,” Mr. Erdogan said. “But now I am recovered and in a better condition.”

No journalists were inside the mosque when the incident happened. But one reporter who was waiting outside said that, according to witnesses he interviewed, the president slumped to his left and was immediately caught by his guards.

Continue reading the main story

“He did not collapse,” said the reporter, Aziz Ozen, who works for Hurriyet, one of Turkey’s leading newspapers. “He just leaned to his left, and they got him right away.”

A government official declined to provide any more details on the incident, instead offering a Turkish news report saying that the president had fainted.

According to Turkish protocol, if Mr. Erdogan had been incapacitated for a longer period of time, he would have been temporarily replaced by the speaker of the Turkish Parliament, Ismail Kahraman, a lawmaker from Mr. Erdogan’s party.

In metaphorical terms, however, Mr. Erdogan’s absence would leave a void. He has been the central figure in Turkish politics for a decade and a half, and he has succeeded in isolating most of his rivals, both within his party and outside it.

His son-in-law, Berat Albayrak, Turkey’s energy minister, is often mentioned as a potential successor. But he lacks Mr. Erdogan’s personal appeal.

Mr. Erdogan’s health scare occurred at the end of the month of Ramadan, when Mr. Erdogan, a Muslim, had been fasting during daylight hours.

It follows a series of diplomatic crises involving Mr. Erdogan’s government. In recent weeks, Turkey has sided with Qatar in its spat with most of its neighbors, including Saudi Arabia and the United Arab Emirates, which are angered by Qatari foreign policy.

In a show of solidarity, Mr. Erdogan’s government agreed to send more Turkish troops to join those already in Qatar. After Saudi Arabia criticized the move, Mr. Erdogan reacted angrily on Saturday, calling the Saudis “disrespectful.”

Mr. Erdogan is also angry with the United States. In Syria, the American government is working with Syrian Kurdish militias whom Turkey views as terrorists. In Washington, American officials have issued arrest warrants for a group of Mr. Erdogan’s bodyguards who were filmed assaulting protesters during Mr. Erdogan’s visit last month.

That furor has now threatened to add a new tension to Turkish-German relations. There have been reports in the German news media suggesting that the German government had told Turkey the bodyguards involved in the Washington incident would not be welcome in Hamburg for a Group of 20 summit meeting in early July.

Officials in Berlin declined on Monday to confirm the news reports. But Martin Schäfer, a spokesman for the Foreign Ministry, said that he could “assume with a good conscience that these people who have been incriminated by American judicial authorities won’t set foot on German soil in the foreseeable future, including during the G-20 summit.”

Ralf Martin Meyer, the chief of police in Hamburg, told the German newspaper Bild on Monday that a “clear message” had been sent to Turkish officials “that we will not accept something like this,” he said, referring to the incident in Washington.

Some 15,000 police officers are expected to be deployed to secure the streets of Hamburg during the international summit meeting, the first in more than a decade to be held in a German city. Hamburg has a long tradition of extreme leftist groups and a lively anarchist scene that has been plotting for months to disrupt the arrival of the delegates.

Hamburg is also home to roughly 90,000 Turks and their descendants, many of them ethnic Kurds. That has prompted worries about possible clashes between Mr. Erdogan’s supporters and opponents, beyond the general disruption sought by leftist organizers.

Mr. Meyer said that German police officers would not hesitate to detain anyone involved in clashes, regardless of their motivation. “We would move very swiftly and very clearly against this,” the police chief said. “Here on the streets of Hamburg, we alone have such authority.”