The violence has continued despite Brazil's deployment of 4,000 troops to combat death squads in Para state.

Two rural workers and a union leader were killed in the three days after Stang was murdered on Feb. 12, and human rights workers, unionists and land activists say they have received new threats.

Two ranchers were gunned down on Monday night. Police were unable to say if the killings were linked to land battles.

Police on Tuesday said they found a .38 revolver used in Stang's murder in the house of rancher Vitalmiro Bastos de Moura in the vicinity of Anapu -- a poor jungle town 30 miles (50 km) from where Stang was shot six times on a jungle track.

The murder of the prominent human rights activist as she opposed illegal loggers and ranchers encroaching on a state-run peasant settlement caused world outrage and embarassed the federal government. She had frequently warned of death threats to farmers and activists. The US government has pressured Lula to find her killers.

Troops caught a third suspect in the contract killing, Clodoaldo Carlos Batista, late Monday as he tried to take a ferry across the Xingu river in the region where she was shot.

Rayfran das Neves Sales, another suspect, has confessed to shooting Stang and named others involved.

Authorities suspect Bastos paid two gunmen and an intermediary $19,300 to kill the nun. He is still on the run.

RURAL CIVIL WAR

Lula accelerated creation of environmental protection areas and federal posts on the Amazon frontier to block the advance of illegal loggers and farmers and punish them financially.

Stang was setting up such an area when she was shot.

"The killing of the missionary and the unionists was a calculated action by some businessmen in the timber industry who oppose our actions in Para," Lula told peasant farmers in the state of Mato Grosso do Sul in southeastern Brazil.

A congressional investigation into the killings said they are part of a "rural civil war" in Para.

"These are private militias operated by large landowners, loggers ... to eliminate any resistance," said ruling Workers' Party deputy Luiz Couto, who heads the investigation.

"There is a lot of tension," said Henry des Roziers, a lawyer for the Catholic human rights group Stang worked for.

Like Stang, des Roziers is on a death list. The price on his head is $39,000, according to local press reports.

The federal government has sent federal police teams to run the Stang investigation. Such crimes often go unpunished in rural areas of Para where judges and police are in league with timber mafias and land barons.