ISTANBUL — A strong earthquake struck Friday in the Aegean Sea between the Turkish coast and the Greek island of Samos, killing at least 19 people and injuring over 700 amid collapsed buildings and flooding, officials said.

A small tsunami struck the Seferihisar district south of Izmir, the city in western Turkey that was the worst affected by the quake, said Haluk Ozener, director of the Istanbul-based Kandilli Observatory and Earthquake Research Institute.

At least 17 people were killed in Izmir, Turkey’s third-largest city, including one who drowned, and 709 were injured, according to Turkey’s Disaster and Emergency Management Presidency, or AFAD.

Among the dead were the wife and two children of the secretary-general of the Turkish Medical 1Association’s Izmir branch, the group said.

On Samos, two teenagers died after being struck by a wall that collapsed. Greek Prime Minister Kyriakos Mitsotakis tweeted condolences, saying “Words are too poor to describe what one feels before the loss of children.”

At least 19 people were injured on the island, with two, including a 14-year-old, being airlifted to Athens and seven hospitalized on the island, health authorities said.

The small tsunami that hit the Turkish coast also affected Samos, with seawater flooding streets in the main harbor town of Vathi. Authorities warned people to stay away from the coast and from potentially damaged buildings.

Izmir Gov. Yavuz Selim Kosger said at least 70 people were rescued from wrecked buildings, with four destroyed and more than 10 collapsed. Others suffered less severe damage, he said, but did not give an exact number.

Search-and-rescue efforts were underway in at least 17 buildings, AFAD said. Turkish media showed rescuers pulling people from the rubble, including one survivor who was found about six hours after the quake. Emergency teams continued digging after nightfall and cranes lifted concrete slabs from the wreckage.

The earthquake, which the Kandilli Institute said had a magnitude of 6.9, struck at 2:51 p.m. local time in Turkey and was centered in the Aegean northeast of Samos. AFAD said it measured the magnitude at 6.6.

It was felt across the eastern Greek islands and as far as the Greek capital, Athens, and in Bulgaria. In Turkey, it shook the regions of Aegean and Marmara, including Istanbul. Istanbul’s governor said there were no reports of damage in the city, Turkey’s largest.

Video on Twitter showed flooding in the Seferihisar district, and Turkish officials and broadcasters called on people to stay off the streets after reports of traffic congestion. Izmir Mayor Tunc Soyer urged residents to not enter damaged buildings and to be mindful of social distancing and mask mandates amid the COVID-19 pandemic.