* Quake of up to 7.0 magnitude felt in Turkey, Greece
* Buildings collapse in Izmir province
* Some people trapped in rubble
* High tidal wave warnings in place in Greek island of Samos.
ISTANBUL, Oct 30 (Reuters) - A strong earthquake struck the Aegean Sea on Friday and was felt in both Greece and Turkey, where some buildings collapsed in the coastal province of Izmir and a government minister said people were trapped in rubble.
People crowded onto the streets in Izmir city, witnesses said, after the quake struck with a magnitude of up to 7.0. The tremor could be felt as far away as in Istanbul and on Greek islands, where officials said some people were panicking although there were no immediate reports of injuries.
There were various reports of damage to property, with Turkish Interior Minister Suleyman Soylu saying six buildings had collapsed in two districts of the coastal city of Izmir.
Urbanisation Minister Murat Kurum put the number of collapsed buildings in the area at five, and added that some people were stuck under the rubble. Izmir mayor Tunc Soyer said nearly 20 buildings had collapsed in the province.
In a tweet, Soylu said there were no reports of casualties from six other provinces where the earthquake was felt but added there were small cracks in some buildings.
Ilke Cide, a doctoral student who was in Izmir's Guzelbahce region during the earthquake, said he went inland after waters rose after the earthquake.
"I am very used to earthquakes... so I didn't take it very seriously at first but this time it was really scary," he said, adding the earthquake had lasted for at least 25-30 seconds.
Crisscrossed by major fault lines, Turkey is among the most earthquake-prone countries in the world. More than 17,000 people were killed in August 1999 when a 7.6 magnitude quake struck Izmit, a city southeast of Istanbul. In 2011, a quake in the eastern city of Van killed more than 500.
Turkey's Disaster and Emergency Management Presidency (AFAD) said its teams had been sent to the region of Friday's quake.
Residents of the Greek island of Samos, which has a population of about 45,000, were urged to stay away from coastal areas, Eftyhmios Lekkas, head of Greece's organisation for anti-seismic planning, told Greece's Skai TV.
"It was a very big earthquake, it's difficult to have a bigger one," said Lekkas.
High tidal wave warnings were in place in Samos.
"We have never experienced anything like it," said George Dionysiou, the local vice-mayor. "People are panicking." A Greek police spokesman said there was damage to some old buildings on the island, with no immediate reports of injuries.
AFAD put the magnitude of the earthquake at 6.6, while the U.S. Geological Survey said it was 7.0. It struck at around 1150 GMT and was felt along Turkey's Aegean coast and the northwestern Marmara region, media said.
The epicentre was some 17 km (11 miles) off the coast of the Izmir province, at a depth of 16 km, AFAD said. The U.S. Geological Survey said the depth was 10 km and that the epicentre was 33.5 km off Turkey's coast.
(Reporting by Ali Kucukgocmen and Ece Toksabay; Additional reporting by Renee Maltezou, Angeliki Koutantou and Michele Kambas; Editing by Ezgi Erkoyun, Dominic Evans, Jon Boyle and Susan Fenton)
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