Six dead, buildings collapse as major earthquake hits Turkey
The US Geological Survey said the 7.0 magnitude quake was registered 14 kilometres (almost nine miles) off the Greek town of Karlovasi on Samos.
The Turkish government's disaster agency reported a lower magnitude of 6.6 for the quake while Greece's seismological agency said it measured 6.7.
Much of the damage in Turkey occurred in and around the Aegean resort city of Izmir, which has around three million residents.
Woman pulled out alive
Images from the popular vacation destination showed collapsed apartment buildings and dazed people trying to make their way through rubbled piled high on the streets.
"Oh my God!" one passerby shouted near a collapsed building in one image that went viral in Turkey.
In another, a crowd let out a relieved cheer and broke out in applause as one woman was pulled out alive in tears.
Izmir's mayor Tunc Soyer told CNN Turk that 20 buildings had collapsed, with officials saying they were focusing their rescue efforts on 12 of them.
Turkey's disaster agency reported the death of six people, and said that more than 200 were injured.
But scenes of devastation suggested the toll could rise.
Rescuers using chainsaws
Images on social media showed water rushing through the streets of one of the towns near Izmir from an apparent sea surge.
Thick white plumes smoke rose from various parts of the city itself, where buildings had collapsed.
Aerial footage on Turkey's NTV television showed entire city blocks turned to rubble.
Footage showed rescuers being helped by residents and police using chainsaws as they tried to force their way through the rubble of a seven-floor building that had collapsed.
Rescuers called for silence for signs of any survivers, clearing boulders and other debris in a human chain.
As the hours wore on, the region's governor Yavuz Kosger said 70 people had been pulled out of the rubble alive.
Turkish President Recep Tayyip Erdogan tweeted that he was ready to help "with all the means available to our state".
'It was chaos'
On the Greek island of Samos, near the quake's epicentre, people rushed out into the streets in panic.
"The walls of some houses have crumbled and several buildings are damaged," the island's deputy mayor Michalis Mitsios was quoted as saying by public broadcaster ERT.
"It was chaos," added fellow deputy mayor Giorgos Dionysiou. "We have never experienced anything like this."
The Greek civil protection agency told Samos residents in a text message to "stay out in the open and away from buildings".
Greece and Turkey are both situated in one of the world's most active earthquake zones.
The two uneasy neighbours also suffer from historically poor relations despite both being members of the NATO military alliance.
But the quake saw a spurt of what pundits immediately termed "earthquake diplomacy", after the two countries' leaders and foreign ministers promising to help each in rare phone calls.
"I just called President @RTErdogan to offer my condolences for the tragic loss of life from the earthquake that struck both our countries. Whatever our differences, these are times when our people need to stand together," Prime Minister Kyriakos Mitsotakis said on Twitter.
Greece and Turkey are "ready to help each other in case of need", the Turkish foreign ministry said after a phone call between Greek Foreign Minister Nikos Dendias and his counterpart Mevlut Cavusoglu.
Top Erdogan aide Fahrettin Altun tweeted that the disaster "reminds us once again how close we are despite our differences over policy".
Some of the world's strongest earthquakes have been registered along a fault line that runs across Turkey to Greece.
In 1999, a 7.4 magnitude earthquake struck Turkey's northwest, killing more than 17,000 people, including 1,000 in Istanbul.
Another quake in 2011 in the southeastern province of Van resulted in more than 600 deaths.
In Greece, the last deadly quake killed two people on the island of Kos, near Samos, in July 2017.