A major earthquake in the Aegean Sea rattled parts of Greece and western Turkey on Friday, leveling structures in the western Turkish city of Izmir and severely damaging several residential buildings.
No information was immediately available about injuries, a Turkish government official said. But Murat Kurum, the environment minister, said in televised remarks that there were reports of people trapped under debris, many of them in the Bayrakli neighborhood of Izmir, which has a population of more than four million.
The earthquake, which registered as magnitude 7.0, according to the United States Geological Survey, was centered off Samos, a Greek island near the Turkish coast, according to Turkey’s disaster management agency.
The quake was felt in Istanbul, about 200 miles northeast of Izmir, and in parts of Greece.
At least six buildings were destroyed in Izmir, Suleyman Soylu, the interior minister, said in a tweet, although the city’s mayor put the number of destroyed buildings closer to 20. Mr. Soylu said there were no initial reports of casualties from nearby cities.
The I.H.H. Humanitarian Relief Foundation said on Twitter that it had sent a 250-person search-and-rescue team to the area.
Footage aired by the Turkish news agency DHA showed at least one building flattened and people climbing atop the debris to shout for survivors in the rubble.
Images posted to social media showed panicked residents running into the street and severely damaged buildings teetering precariously. In one, it appeared that several apartments in a six-story building had collapsed in on one another.
Teoman Cüneyt Acar, a resident of Izmir who felt the quake, told Haber Turk TV that the tremor lasted for around 45 seconds, and others said objects in their apartments had toppled over and walls cracked.
On the Greek island of Samos, residents poured onto the streets, with many posting photos and videos on social media showing the main port flooded.
Two text messages were sent out by Greece’s General Secretariat for Civil Protection using a European emergency alert system, with the “Extreme alert” designation warning people on several islands in the triangle formed by Ikaria, Kos and Chios to avoid the coastline due to the risk of a possible tsunami and to stay away from buildings because of possible aftershocks.
The second message was sent to residents of Samos, urging them to remain outdoors in safe areas away from buildings.
Niki Kitsantonis contributed reporting.