SAN SALVADOR (Reuters) - Four inmates at a prison in El Salvador were murdered on Saturday amid a fight between inmates, the national prison service said via Twitter.

The inmates, members of the Barrio 18 gang, were killed in the facility which is in the city of Quezaltepeque, 21 km (13 miles) northwest of the capital.

The attorney general's office said that the death toll could rise.

In August last year, 14 inmates were killed in the prison, with authorities saying it was part of a purge within the same gang.

(Reporting by Nelson Renteria; Editing by Robert Birsel)