Iran closed its airspace to commercial flights for several hours early Thursday without explanation, as tensions with the United States escalated over Tehran’s violent crackdown on nationwide protests.

The closure lasted more than four hours, according to pilot notices, affecting a major East-West flight corridor. International airlines rerouted flights north and south of Iran, and after one extension, the airspace reopened, with several domestic flights airborne by around 7 a.m.

Iran has previously restricted its airspace during conflicts, including the 12-day war with Israel in June and the Israel-Hamas war. Although there were no immediate signs of hostilities this time, the move disrupted global aviation due to Iran’s strategic location on key flight routes.

“Several airlines have already reduced or suspended services, and most carriers are avoiding Iranian airspace,” said SafeAirspace, a website that tracks aviation risks. The site warned that the closure could indicate heightened security or military activity, raising the possibility of missile launches or misidentification of civilian aircraft.

The alert recalled Iran’s 2020 downing of Ukraine International Airlines Flight PS752, when air defenses misidentified the plane as a threat, killing all 176 passengers.

The airspace closure coincided with U.S. precautions in the Gulf, including evacuation advice for personnel at a key U.S. military base in Qatar and a temporary halt on U.S. personnel movements to military installations in Kuwait. The U.N. Security Council scheduled an emergency meeting on Iran at the U.S.’s request.

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U.S. President Donald Trump gave vague remarks Wednesday, saying he had been told executions in Iran had been halted, without providing further details. Trump had earlier assured Iranian protesters that “help is on the way” and that his administration would act in response to the crackdown.

Iranian Foreign Minister Abbas Araghchi called for diplomacy over conflict, saying, “Between war and diplomacy, diplomacy is a better way, although we don’t have any positive experience from the United States.”

The developments came hours after Iran’s judiciary chief urged swift action against thousands of detainees. Activists warned that executions could occur soon. According to the U.S.-based Human Rights Activists News Agency, at least 2,615 people have died during the protests, marking the deadliest unrest in Iran in decades and evoking memories of the 1979 Islamic Revolution.