MARACAY, VENEZUELA -- Calling itself the most labor-friendly government in Latin America, President Hugo Chávez's socialist administration has repeatedly increased the minimum wage, turned over the management of some nationalized companies to workers and fostered the creation of new unions.

But labor leaders and human rights groups say the government's efforts have had a dark side. About 75 union members have been shot dead in the past two years as the new unions -- many of them pro-Chávez -- and traditional unions battle it out, making Venezuela among the world's most dangerous countries for labor activists.

"The state is responsible for all these deaths," said Orlando Chirinos, a former Chávez ally who helps lead a labor federation that has seen several members killed in this northern city. "When union leaders from parallel unions know of job sites, they sit there and wait -- and they are all armed. Everyone knows. Why doesn't the government send troops?"

Union leaders and the respected Provea rights group in Caracas say newly formed unions have turned to paid killers, targeting low-level activists and union chiefs alike.

Pedro Perez, a union activist here who was shot in March, said the violence stems from new unions trying to sideline old ones like his.

"They have already killed several friends," said Perez, who now walks with a limp. "You can't be a unionist in this country anymore."

Most of the deaths have taken place in the lucrative construction industry. In exchange for jobs, workers are forced to pay kickbacks to union bosses.

With big profits at stake, and the state doing little to control the violence, the number of killings has tripled from 12 four years ago to 34 recorded in the 12 months ending in May, according to the Catholic Church's human rights unit. Though Colombia, with its slow-burning conflict, has historically recorded the most union slayings in the world, Venezuela appears to have surpassed its neighbor in the past two years and registered more.

And unlike Colombia, where teams of prosecutors, investigators and judges have been deployed to resolve cases, Venezuela's judicial system has brought only a handful of killers to justice, according to the human rights arm of the Organization of American States. The killings have also failed to garner much attention in Venezuela or with international labor groups.

"There is great indifference, combined with great impunity," said Marino Alvarado, an investigator with Provea who is compiling information about the killings, including three more this month.

Calls to the attorney general's office and the Labor Ministry were not returned. But Francisco Torrealba, a deputy in Venezuela's congress and president of a subcommittee on labor issues, acknowledged the problem and said government officials have met with labor federations to stem the violence.

Torrealba said the killings spring from a culture of violence at unions long tied to Venezuela's two traditional anti-Chávez parties. "It's about intra-union violence and has to do with the culture of doing things in this country in a violent way," he said, disputing assertions that the violence has picked up dramatically under Chávez.

Torrealba, president of a pro-government federation representing railway workers, also said that through wage increases and the job security offered at state companies, the Chávez government has "proven itself to be a workers' government."

But Human Rights Watch, which carried out a study of Venezuelan labor, says the government intervenes in union elections and favors pro-government unions in negotiations, sometimes sidestepping larger, established unions for smaller organizations that support Chávez.

Union leaders here say the government is trying to ensure that unions are solidly pro-government, thus bringing practically all important institutions in Venezuela, save for the Catholic Church, under the state's fold.

Already, the Venezuelan Workers Confederation, a decades-old umbrella for most unionized workers, has suffered a dramatic loss of influence since it participated in anti-government marches that led to Chávez's brief ouster in 2002.

The newcomers include several federations and 4,000 new unions, up from 1,300 in 2001, said Froilan Barrios, among the directors of the Workers Confederation and a labor scholar.

In this city of 1.3 million just west of Caracas, the leaders of UNT, a federation representing 80 unions, contend that the killings of eight union activists in the past five years is designed to weaken their movement.

"We believe it is political, to debilitate UNT and cut us off from projecting ourselves," said Emilio Bastidas, a regional coordinator for the federation.

The killings, he and other union leaders said, have the makings of professional hits. One union activist was shot in his home. Three others died at a roadside stand in 2008 when two men calmly emptied their weapons into them and then fled.

Among the most recent victims was Jerry Diaz, 35, who was shot twice on April 25, moments after he got into his car at his home.

His twin brother, Cherry Diaz, also a union activist, found him bleeding to death. He is not sure why his brother was killed, but he recounted how a new union has tried to muscle in on their longtime union at a paper company.

"This is becoming like a hobby here in Aragua state," Diaz said of the violence. "What we are sure about is that they are now turning to hit men, to assassinate."