MEXICO CITY (Reuters) - An earthquake alarm sounded in Mexico City late on Friday and mild shaking was felt in parts of the capital, according to Reuters witnesses, but there were no immediate reports of any damage or injuries.

In a preliminary report, Mexico's seismological service estimated the quake's magnitude at 6.3, with its epicenter near the town of Matias Romero in southern Oaxaca state.

The U.S. Geological Survey (USGS) put the magnitude lower at 5.9 but at roughly the same location. The USGS said the quake struck at a depth of 67 miles (108 km).

(Reporting by Dave Graham; Editing by William Mallard)