Brasilia, May 27 (IANS): At least 15 people have been killed in fighting between inmates at a prison in northern Brazil, officials said.

The clashes reportedly broke out on Sunday during visiting hours at Anísio Jobim Penitentiary Complex in Manaus, the BBC reported.

Some of the victims were stabbed with sharpened toothbrushes in front of visitors, while others were strangled to death.

"It was total chaos. Everyone started to run and everyone was pounding on the cell gates, at the doors and running down the aisles," the mother of an inmate told the Rio Times.

Officials said that the violence was later contained and an investigation was launched into the cause of the struggle.

In Brazil, attempts to reform the prison system and to introduce tighter controls have met resistance from powerful criminal gangs which operate both inside and outside of jails.

The incident comes only two years after infighting killed 56 at the same jail, one of the deadliest riots ever in a Brazilian prison.

Brazil has the world's third-largest prison population -- 712,305 inmates in April this year, according to official figures.