A strong magnitude-7.3 earthquake struck off the coast of El Salvador and a tsunami warning was issued but there were no immediate reports of damages or injuries, authorities said early Monday.

A tsunami warning was in effect for Costa Rica, Nicaragua, El Salvador, Honduras, Guatemala, Panama and Mexico after the quake struck at 10:37 p.m. Sunday. But David Walsh, an oceanographer with the Pacific Tsunami Center in Ewa Beach, Hawaii, said a minor, 20-centimetre (7.8-inch) swell was registered off Acajutla, El Salvador.

The quake was located 86 miles (138 kilometres) south-southwest of San Miguel, the U.S. Geological Survey reported on its website. The temblor took place at a depth of 32.9 miles (53 kilometres).

Alfonso Lara of El Salvador's Civil Protection agency said authorities were alerted to the threat of a tsunami. ``We are doing a general monitoring of the entire coast through our technicians and representatives,'' he said.

The tsunami warning has since been cancelled.

(The Associated Press)