This U.S. Geological Survey map shows the area of the underwater earthquake.

The U.S. Geological Survey is reporting that a magnitude 7.3 underwater earthquake has struck off the coast of El Salvador, killing at least one person but there were no immediate reports of major damage.

El Salvador's emergency services said a dozen homes in the department of Usulutan had been slightly damaged but that coastal areas appeared calm and the country's international airport was unaffected.

The agency urged people living near the coast to move inland after placing a tsunami alert in effect. Nonetheless, they said via their Twitter account that waters in coastal areas appeared calm.

Local reports indicate the quake was felt throughout Central America, but there are no immediate reports of injuries or damage outside El Salvador. Emergency services in Nicaragua, Honduras and Guatemala as well as in Panama said they had no early reports of damage or injuries. Nicaraguan presidential spokeswoman Rosario Murillo urged coastal residents to seek out higher land in case of a tsunami.

The quake struck 42 miles west-southwest of Jiquilillo off the coast of San Salvador and Nicaragua, the U.S. Geological Survey said. It said the quake hit at a depth of 25 miles and occurred as the result of normal faulting in the Central America subduction zone.

Wilfredo Salgado, mayor of the city of San Miguel in El Salvador, said on his Twitter account that a man was killed when an electricity post fell on him.

"It felt really powerful, suddenly the whole house started to move," said Xiomara Amaya, 30, who lives in El Salvador's department of Usulutan.

The Pacific Tsunami Warning Center at one point warned of possible tsunami waves in the region but then said there was no threat.

In 2001, two powerful earthquakes struck El Salvador for a month apart killing more than 1,150 people between them, and leaving hundreds of thousands homeless.

Two years ago, a 7.3 magnitude earthquake struck in the Pacific Ocean off El Salvador, triggering a brief tsunami warning but causing no major damage or casualties.

Al Jazeera with wire services