A powerful earthquake has shaken central and southern Mexico.

The US Geological Survey calculated its magnitude at 7.5 and said it was centred near the Pacific resort of Acapulco, where many Mexicans are vacationing for the Easter holiday.

An AP reporter said it was felt strongly in the resort city but there were no immediate reports of injuries or damage.

The quake shook Mexico City for at least 30 seconds, with buildings swaying as people fled high rises and took to the streets.

Because of the Easter holiday, that city was less crowded than usual.

Mexico City is vulnerable even to distant earthquakes because much of it sits atop the muddy sediments of drained lake beds that quiver as quake waves hit.

The magnitude-8.1 quake in 1985 that killed at least 6000 people and destroyed many buildings in Mexico City was centred 400km away on the Pacific Coast.