Police fired rubber bullets to try to separate two groups of inmates as they fought a pitched battled in the courtyard of the Alcacuz prison in the northern town of Natal, AFP reporters overlooking the facility saw.
The governor of the surrounding Rio Grande do Norte state, Robinson Faria, called for the armed forces to deploy in the streets of Natal after rioting spread beyond the prison.
Globonews television channel showed pictures of injured inmates being evacuated from the jail.
Rioting also broke out in six towns in the state, a spokesman for local authorities told AFP.
Six cars and a truck were set on fire and seven people were arrested in that unrest, the spokesman said.
One person died and five were hurt during another prisoner uprising in the nearby town of Caico, he said.