QUITO, March 28 (Xinhua) -- Three inmates were killed and six others injured in a riot at Ecuador's second-largest penitentiary, the Guayaquil regional prison, the national prison management service SNAI said Thursday.

"After four hours of clashes, on Wednesday at 11 p.m. local time (0400 GMT Thursday), the security forces managed to neutralize the situation," the agency said in a statement, referring to the National Police and Armed Forces, which are in charge of safeguarding the prison.

One of the injured has been admitted to a healthcare facility and five others were sent back to the prison after receiving medical attention.

The riot stemmed from an "internal revolt by a group of inmates," the security forces said in a statement, without providing more details.