An earthquake has struck off the coast of El Salvador and Nicaragua overnight and was felt across Central America, killing at least one person but there were no immediate reports of major damage.

The earthquake was measured at magnitude 7.3 and 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.

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 Usulutan.

 The quake struck 67km west-southwest of Jiquilillo in Nicaragua and 174 km southeast of San Salvador, the US Geological Survey said. It said the quake hit at a depth of about 40 km.

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

In 2001, two powerful earthquakes a month apart killed more than 1,150 people and left hundreds of thousands homeless.

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