MEXICO CITY (REUTERS) - A magnitude 6.1 earthquake shook Mexico City on Wednesday, its epicentre located in the poor southern state of Guerrero, the United States Geological Survey (USGS) said, but there were no immediate reports of damage or injuries.

Buildings swayed for around a minute in Mexico City, and several offices evacuated staff.

The epicenter was 18km north-west of the town of Ayutla de los Libres, the USGS said, inland from Mexico's Pacific coast and the popular tourist resort of Acapulco.

It said the tremor struck at a depth of 34.8 km. The USGS initially reported the quake at 6.4 magnitude, but then revised down the reading.

Mexico City Mayor Miguel Angel Mancera said on Twitter that there were no immediate reports of injuries or damage in the capital.