At least 30 people were killed in a prison riot in the city of Natal, officials said on Sunday. According to reports, the riots started when one group of inmates invaded cellblocks run by a rival faction.

"There are probably more than 30 dead," police investigator Otacilio de Medeiros told reporters after leaving the prison. Another source told Reuters news agency that the death toll could "slightly rise further."

Prison officials "could see the heads ripped off" of three inmates, news website Folha de Sao Paulo cited the prison manager Zemilton Silva as saying.

The military police and firefighters set up a perimeter around the prison in the country's northeast, with officers managing to enter the building and restore control over the prison complex after 14 hours of violence.

Gang war ups the ante

The Natal clashes are the latest episode in the war between Primeiro Comando da Capital (PCC) gang and its rivals, likely including Brazil's oldest gang, Comando Vermelho, and its apparent ally Familia do Norte (FDN).

Some 100 prisoners have been killed in the wave of prison violence since the beginning of January. The first riot claimed the lives of 56 inmates in the northern state of Amazonas after the New Year. Many of the victims were beheaded and dismembered. Last week, 33 prisoners were also brutally murdered in a clash in the neighboring state of Roraima, with bodies showing signs of mutilation.

With several powerful crime syndicates active in the country, Brazil struggles with overcrowded prisons, housing over 622,000 people in facilities designed to take less than 372,000.

rs, dj/tj (dpa, AP, AFP, Lusa)