People were trapped inside various buildings that caught fire in Mexico City, a civil protection official told local TV.
The quake caused buildings to sway sickeningly in Mexico City and sent panicked office workers streaming into the streets, but the full extent of the damage is not yet clear.
Mexican media broadcast images of several collapsed buildings in heavily populated parts of the city.
The U.S. Geological Survey said the quake was centred near the Puebla state town of Raboso, about 123 kilometres southeast of Mexico City.
Twelve days ago, shortly before midnight on Sept. 7, an 8.1 magnitude earthquake hit Mexico, killing almost 100 people.