Washington: A strong 7.3 earthquake shook an area in the Pacific Ocean off the coast of El Salvador early Monday, generating a potentially destructive tsunami that is threatening Central America and Mexico, US authorities said.

The epicentre of the tremor, which occurred at 0437 GMT, was located 111 kilometres south of the city Puerto El Triunfo in El Salvador, according to the US Geological Survey.

Following the quake the Pacific Tsunami Warning Center issued an alert, saying that the temblor, which took place at a depth of 54 kilometres, had spawned a tsunami.

“Sea level readings confirm that a tsunami was generated,” the centre said, pointing out that the threat extended to all Central American nations and Mexico.

It warned that this tsunami may be “destructive along the coastlines of the region”.

According to the centre, locations like Cabo San Elena and Puerto Quepos in Costa Rica, Corinto and Puerto Sandino in Nicaragua and Acajutla in El Salvador were among those that faced the danger first.

“Authorities in the region should take appropriate action in response to this possibility,” the center said.

No reports of casualties or damage were immediately available.

But in El Salvador, Civil Protection Service Director Jorge Melendez dismissed the tsunami threat.

“There is no tsunami alert,” he told AFP in San Salvador. “The US Geological Survey has recorded a 7.4-point earthquake, but our observatory here recorded just a 5.7-point tremor.”

The earthquake reading was based on the open-ended Moment Magnitude scale used by US seismologists, which measures the area of the fault that ruptured and the total energy released.

The initial USGS report put the strength of the quake at 7.4, but it was later revised to 7.3.