Quito,  At least two people have been killed and 18 injured in a series of clashes this week between rival criminal rings at the Litoral Penitentiary in the Ecuadorian port city of Guayaquil, police said.

Clashes broke out on Tuesday and continued through Thursday after police began the process of transferring 1,002 prisoners from the country's largest prison to other penitentiaries, reports Xinhua news agency.

In an updated report on the riots, the police said two inmates have been killed and 18 others injured, including six prisoners, nine police officers and three military personnel.

Victor Zarate, commander of National Police Zone 8, which includes the city of Guayaquil, told local media that 700 police officers from tactical units and 470 Armed Forces troops intervened to regain control of the prison.

The uniformed officers met with violence and armed attacks, and responded with force, he said.

Meanwhile, the State Prosecutor's Office tweeted that it has started a preliminary investigation into the incidents.