Two strong undersea earthquakes shook a major port city in western Turkey on Monday, damaging buildings, prompting terrified residents to run from their homes and jump from windows, and injuring at least six people, officials and news reports said.

The quakes, which registered preliminary magnitudes of 5.7 and 5.9, struck at 8:45 a.m. and 12:47 p.m., said Gulay Barbarasoglu, head of the Istanbul-based Kandilli Observatory (search). Both were centered in the bay of Sigacik (search), about 30 miles southwest of the Aegean port city of Izmir (search), Turkey's third-largest city with a population of about 3 million.

Three people were injured in Izmir when they jumped from windows or balconies in panic, local officials said. Another three people were injured in nearby Urla, the Anatolia news agency reported.

There were no immediate reports of damage in the ancient city of Ephesus, about 60 miles south of Izmir.

The first quake collapsed the walls of some houses and shattered windows in Urla, west of Izmir, private NTV television said. Mayor Selcuk Karaosmanoglu told Anatolia the quake toppled some chimneys in the village of Bademler and cracked some buildings in the town center.

The second quake caused further damage, smashing windows, witnesses said.

Authorities evacuated schools and in some areas broadcast music through loudspeakers to calm panicking students. Authorities later decided to close schools for two days.

Scientists warned there could be more quakes and aftershocks during the next few days and urged residents to stay away from damaged buildings.

The quakes also shook the Greek islands of Chios, Samos and Ikaria, but no damages or injuries were reported. The Athens Geodynamic Institute (search) gave a different measurement of the first quake's strength, saying it had a magnitude of 6.

Quakes are frequent in Turkey, which lies on the active North Anatolian fault. Ruptures in the fault caused two quakes in 1999 that killed some 18,000 people and devastated large parts of northwestern Turkey.