SAN SALVADOR (AFP) - A strong 6.5-magnitude earthquake struck the territories of southern Guatemala and El Salvador Friday, United States seismologists said, though officials said there were no immediate reports of casualties or damage.

The US Geological Survey (USGS) said the quake struck just 6km from Pajapita, Guatemala at a depth 67.7km 12.13am Greenwich Mean Time.

The Environmental Observatory in San Salvador said the quake was centred on the coast of Guatemala and Mexico, measuring its strength slightly lower at 6.3 on the Richter scale.

A second quake measuring 5.5 in magnitude occurred seven minutes later, according to the Observatory, with its epicentre in the Pacific waters of Guatemala.

"We have no reports of any damage," so far, Mr Jorge Melendez, El Salvador's director of civil protection, said on national radio.

The USGS said in its bulletin on the first quake that it was just 20km north-east of Suchiate, a municipality in the Mexican state of Chiapas, on the border with Guatemala.