President Claudia Sheinbaum was forced to evacuate the presidential palace during her regular morning press conference, along with the journalists in attendance, when the earthquake alert sounded.

The Seismological Service said that the earthquake's epicenter was situated 14 kilometers (nine miles) southwest of San Marcos, in the southern state of Guerrero, about 400 kilometres from Mexico City.

The US Geological Survey said the quake struck around 8:00 am east of Acapulco, a major port and beach resort.

Sheinbaum said there were no immediate reports of major damage in either Mexico City or Guerrero.

Mexico, which is situated between five tectonic plates, is one of the world's most seismically active countries.

Karen Gomez, a 47-year-old office worker living on the 13th floor of an apartment building in Mexico City, told AFP she was roused from her sleep by a street siren.

"I woke up in terror. My cellphone alert said it was a powerful earthquake."

Norma Ortega, a 57-year-old kindergarten director, living in a 10th-floor apartment, said she could feel her building shake.

"I got a terrible fright."

The center of Mexico City is built on the muddy subsoil of what was once the bed of a lake, making it particularly vulnerable to earthquakes.

Those most strongly felt usually originate off Guerrero state on the Pacific coast.

On September 19, 1985, an 8.1-magnitude earthquake devastated a vast swathe of Mexico City, leaving nearly 13,000 dead, mostly in the city, according to official figures.

In 2017, also on September 19, a 7.1-magnitude quake killed 369 people, also mostly in Mexico City.

Early warning systems, including smartphone apps, have been developed to warn Mexico City residents of strong quakes and urge them to reach safety.

The city has also installed loudspeakers on lampposts to broadcast the alerts.