BRASïLIA (AFP) - Negotiators persuaded inmates holding hostages seized during a prison riot in Brazil to free a guard on Sunday, but were still working to free three more guards and 118 prisoners' relatives.

A prison spokeswoman called the guard's release a sign of progress a day after inmates seized 122 people in a riot at the maximum-security Advogado Jacinto Filho prison in Aracaju, the capital of the northeast Sergipe state.

"We're moving forward. They've freed one guard. Three remain, along with the 118 family members," Sandra Melo, a spokeswoman for the prison, told AFP.

"Negotiations are also continuing on the relatives' release. We hope this will be resolved today," she said.

A military police captain is leading the negotiations. A judge and representatives of the state human rights commission are also present at the prisoners' request, said Melo, a lawyer for Reviver, a private firm that co-manages the prison with Sergipe state.

The riot broke out 26 days before the opening match of the World Cup in Brazil, which has faced protests over the more than US$11 billion (S$14 billion) being spent on the tournament and a series of strikes that threaten to disrupt it, including by police.

No World Cup games will be played in Sergipe, however.

The riot erupted in one of the prison's four wings and involved 123 prisoners, officials said. Talks to free the hostages began Saturday but broke off overnight.

Globo TV showed video of a group of prisoners in blue uniforms approaching negotiators.

Melo said the rioters were recently sentenced inmates who had been temporarily jailed at the facility and were demanding to be transferred.

"This is a maximum security prison and they are asking for more flexible rules," she said.

The prison holds 476 inmates and has not faced complaints of overcrowding.

The riot broke out at the end of family visits and was contained by police before it could spread to the prison's other three wings, reports said.

During the fighting, inmates killed a police dog used to search for contraband, officials said.

The head of military police in the state, Mauricio Iunes, told the G1 news website Saturday that the authorities considered the prisoners' relatives to be only "potential hostages."

"We don't believe that the inmates will hurt their own relatives," he said.

However, he said the four prison guards were genuine hostages because "they are being threatened inside there."

A similar riot broke out two years ago at the same prison and was resolved after 26 hours.

In Brazil there are currently 548,000 people in prison - and a need for 207,000 more spots to prevent overcrowding, according to Conectas, an organization specializing in inmate rights.

Late last month, six prisoners died and six were wounded in a riot at a prison in the state of Bahia, which borders Sergipe to the south.