A firefighter walks through the "War of the Worlds" movie set at Universal Studios after a mobilization exercise to prepare for earthquakes and other disasters in Los Angeles, California May 21, 2014. FEMA and the California Governor's Office of
A firefighter walks through the "War of the Worlds" movie set at Universal Studios after a mobilization exercise to prepare for earthquakes and other disasters in Los Angeles, California May 21, 2014. FEMA and the California Governor's Office of Emergency Services were testing the Urban Search
A firefighter walks through the "War of the Worlds" movie set at Universal Studios after a mobilization exercise to prepare for earthquakes and other disasters in Los Angeles, California May 21, 2014. FEMA and the California Governor's Office of Emergency Services were testing the Urban Search & Rescue System by deploying multiple teams. REUTERS/Lucy Nicholson (UNITED STATES - Tags: DISASTER SOCIETY)

A strong 6.9 magnitude earthquake struck Greece and Turkey on Saturday. A total of 266 were injured, mostly from Turkey, caused by panic as people rushed to get out of buildings.

The quake occurred 69 km (42 miles) south-southwest of the Greek city of Alexandroupolis, between the islands of Lemnos and Samothrace, the U.S. Geological Survey (USGS) said. it had a depth of 10 km (6 miles).

The massive temblor was felt in Thessaloniki, the west coast of Turkey and as far away as Bulgaria and Istanbul.

"The earthquake has occurred in an area with especially high seismic activity, which, in the past, has given earthquakes up to 7 magnitude (in 1982)," Manolis Skordilis of the Institute of Geophysics told The Associated Press. "We are currently analyzing the aftershocks and are on alert," he added.

In Greece, one female British tourist was slightly injured at the airport, while two village residents from Kornos were treated for mild injuries at the local hospital, The Greek Reporter said, citing an unidentified Lemnos police officer. The temblor leveled three abandoned houses and a church on Lemnos island.

"It lasted very long and it was very intense. We haven't got the full picture of the damage caused yet," Antonis Chatzidiamantis, mayor of Lemnos, told Mega TV.

In Turkey, the 6.9 magnitude earthquake rattled Istanbul, the Aegean coastal city of Izmir and the popular tourism province of Antalya on the Mediterranean coast. Panic ensued among the people, giving off a tally of 266 injured.

The emergency and disaster management agency of Turkey said close to 70 aftershocks followed, the strongest measuring at 5.5.

"It will certainly have a very rich aftershock activity," Reuters quoted seismologist Costas Papazachos telling Ant1 TV. "There is obviously some reason for concern...we could easily have aftershocks of 5, 5.5 or 6 magnitude," he said.