SAN SALVADOR (Reuters) - Fourteen members of one of El Salvador's most powerful street gangs were killed in a prison on Saturday in what appeared to be an internal gang purge, authorities said.

El Salvador has been racked by rising violence over the past year, with murders surging since the breakdown of a gang truce between the Barrio 18 group and their rivals, the Mara Salvatrucha.

El Salvador's central prison authority said the killings took place in a penitentiary in Quetzaltepeque, some 25 km (16 miles) northwest of the capital San Salvador. The bodies of the victims were found in various parts of the prison.

The correctional facility held around 1,000 inmates, who authorities said were all members of the Barrio 18 gang.

The prison authority described the killings as a "purge action" by the gang, but did not give further details.

The dead are believed to have belonged to a Barrio 18 section known as the "faccion revolucionarios", or revolutionaries' faction, suspected of forcing bus drivers into a violence-plagued strike in late July, the authorities said.

In the year through August 19, about 3,840 homicides had been registered in the Central American country of 6.4 million people, a number just short of the tally for all of 2014.

(Reporting by Nelson Renteria; Editing by Clarence Fernandez)