Imprisoned members of one of Brazil's most notorious organized crime groups on Thursday threatened to kill prison guards if the government does not meet their demands.

Marcos Willians Herbas Camacho, leader of the First Capital Command, known by its Portuguese initials PCC, and 43 other inmates have been on a hunger strike since Monday to protest prison conditions at the Presidente Bernardes Penitentiary, 365 miles west of Sao Paulo.

The gang members said they will try to kill prison guards unless the government makes concessions, said Danilo Bomfim, a spokesman for the Sao Paulo State Prison Guard's Union.

The members said they will remain on strike for 30 days in the Bernardes facility and may spread it into the Presidente Venceslau Penitentiary, 385 miles west of Sao Paulo, for another 30 days.

Detainees threaten prison guards on a daily basis, but authorities are taking the threats more seriously this time because they are coming from the PCC, Bomfim said.

"We can't face these threats as common threats," Bomfim said. "In May and June they became real. We will leave our security posted."

In May, imprisoned gang leaders allegedly ordered outside attacks against police across the city and Sao Paulo state, touching off a weeklong wave of violence that killed nearly 200 police, prison guards, suspected criminals and jail inmates. Two other less deadly waves took place in the following months.

The gang leaders allegedly ordered the attacks because of the anger over a government plan to transfer gang leaders to more secure prisons.