ATHENS, Greece (AP) - A strong earthquake shook southern Greece today, but there were no immediate reports of injuries or serious damage.

The quake, with a preliminary magnitude of 6, had an epicenter under the seabed 75 miles south of the port of Kalamata, the Athens Geodynamic Institute said.

Kalamata was the site of a 1986 earthquake that killed 20 people.

The temblor was felt throughout many parts of the southern Greek mainland. Police in Kalamata said there was no evidence of serious damage or injuries in the city and teams were dispatched to villages to check for any problems.

Experts also were on the alert for any tidal surges because of the strength of the quake - more powerful than last year's 5.9 jolt in Athens that claimed 143 lives and left 100,000 homeless.

Dozens of earthquakes hit Greece every year, but they usually are weak and cause little damage.

Quakes of magnitude 6 can cause severe damage, while a magnitude 7 indicates a major earthquake capable of widespread, heavy damage.