Workers and resident gather at the Angel de la Independencia square after evacuating buildings during a 7.9 earthquake in Mexico City on Tuesday. – Photo by AP

MEXICO CITY: A strong, long 7.6 earthquake with an epicenter in Guerrero state shook central southern Mexico on Tuesday, swaying buildings in Mexico City and sending frightened workers and residents into the streets.

The US Geological Survey set the intensity at 7.6 and said the epicenter was 11 miles underground. Mexico's National Seismological Survey said the temblor had an epicenter southwest of Ometepec and was felt strongly in Oaxaca.

Mexico City Mayor Marcelo Ebrard's Twitter account said the water system and other ''strategic services'' were not experiencing problems.

''I have problems with pressure, I felt I was going to faint,'' said Rosa Maria Lopez Velazquez, 62, outside a mall in Mexico City.

There were no immediate reports of major damage or injuries. Telephone service was down in the city and throughout the area where the quake was felt.