In Brazil, Violence Hits Tribes in Scramble for Land ARAL MOREIRA, Brazil - The gunmen emerged from pickup trucks at dawn, their faces hidden in balaclavas, and stormed into an encampment surrounded by a field of soybean plants near this town on Brazil's porous frontier with Paraguay. Witnesses said the men then shot Nísio Gomes, 59, a leader of the indigenous Guarani people; loaded his corpse onto a truck; and drove away. "We want the bones of my father," said Valmir Gomes, 33, one of Nísio's sons, who witnessed the November attack. He's not an animal to drag away like that. Whether the bodies are hauled away or left as testaments to battles for ancestral land, killings and disappearances of indigenous leaders continue to climb, leaving a stain on Brazil's rise as an economic powerhouse. The expansion of huge cattle ranches and industrial-scale farms in remote regions has produced a land scramble that is leaving the ancestors of Brazil's original inhabitants desperate to recover tribal terrains, in some cases squatting on contested properties. Nonindigenous landowners, meanwhile, many of whom live on land settled decades ago by their own ancestors under the government's so-called colonization programs, are just as attached to their claims. The conflicts often result in violent clashes, which sometimes end tragically for the squatters, armed here only with bows and arrows. Fifty-one Indians were killed in Brazil in 2011; as many as 24 of the killings are suspected of being related to land battles, according to the Indigenous Missionary Council, an arm of the Roman Catholic Church. The killings have focused attention on a problem that still plagues Brazil ahead of the United Nations Conference on Sustainable Development, a gathering of thousands scheduled to be held in Rio de Janeiro this month. Twenty years ago, ahead of the original Earth Summit in Rio, officials responded to international criticism over killings of Yanomami people by gold miners, creating a 37,000-square-mile reserve in the Amazon. In a less striking gesture, President Dilma Rousseff moved ahead this month with the demarcation of seven much smaller indigenous areas. But Cleber César Buzatto, the executive secretary of the Indigenous Missionary Council, said the move was disappointing since the areas were generally not the focus of land battles or big state-financed infrastructure projects. Meanwhile, land clashes in various parts of Brazil are still taking place. In some cases, courts have opened the way for some indigenous people, who account for less than 1 percent of Brazil's population of 191 million, to recuperate lands. In the northern state of Roraima in 2009, Brazil's high court expelled nonindigenous rice farmers from the lands of 20,000 Indians, mainly the Macuxi people. In a case this year, the Supreme Federal Tribunal annulled the private titles of almost 200 properties in the northeastern Bahia State, ruling that the land belonged to the Pataxó Hã-Hã-Hãe people. The decision followed clashes that left at least two dead. But the courts can accomplish only so much. Tension is also increasing over proposed legislation aimed at opening indigenous areas to mining, pointing to how demand for Brazil's natural resources may exacerbate land disputes. Attacks against indigenous peoples persist here in Mato Grosso do Sul, a sprawling state in southwest Brazil where multinationals like Louis Dreyfus, the French commodities giant, have put down stakes. A surge in wealth contrasts with the sense of hopelessness among Mato Grosso do Sul's indigenous peoples, who account for about 75,000 of the state's population of 2.4 million. Their marginalization has roots in policies put in place in the 1930s, when Brazil's rulers corralled the Guarani into small reserves with the intent of opening vast areas to settlers. The results for indigenous people were disastrous. In the shadow of Mato Grosso do Sul's prosperity, indigenous leaders have called attention over the past decade to the deaths of dozens of Guarani children from malnutrition and an epidemic of suicides, notably in Dourados, an urban area where thousands of Guarani live cheek by jowl on small plots of land. "Dourados is perhaps the largest known indigenous tragedy in the world," said Deborah Duprat, Brazil's deputy attorney general. Beyond the malnutrition and suicide, there have also been attacks on the Guarani. More than half of Brazil's killings of indigenous people in 2011 took place in Mato Grosso do Sul. The violence is far from hidden. The November attack on Mr. Gomes, days after he led a group of 200 Guarani who squatted on a soybean farm, was especially brutal. A gang of gun-wielding men, "pistoleiros" as they are called here, was said by witnesses to have carried out the attack, which also involved beatings of others adults and children in the encampment. Brazil's Federal Police found evidence that four landowners in the area had hired a private security firm to remove the Guarani, according to Agência Brasil, the government's news agency. Ten people were identified in December as suspects in the attack, said Jorge Figueiredo, the official investigating the case. More than six months after the attack, the suspects remain free, despite witness accounts of the attack. Mr. Figueiredo said their identities could not be disclosed, as the authorities try to build a stronger case. Moreover, without Mr. Gomes's body, investigators do not even have material proof that he was killed, even though his son Valmir said he saw his father shot dead that day. As the investigation drags on, the Guarani live in fear. Families sleep under tarpaulins in the encampment, which they call a "tekohá," or "sacred land." Teenagers patrol with bows and arrows. When visitors are allowed in, children hold signs saying, "We want the bones of Nísio Gomes, our leader." The sense of impunity over the attack follows a pattern, Guarani leaders said, in which they face landowners who mount powerful legal efforts to oust squatters from their properties. Some landowners contend that Brazil's labyrinthine legal system makes the resolution of disputes difficult. "The rights of all have to be guaranteed," said Roseli Maria Ruiz, whose family owns a ranch that has been partly occupied for more than a decade by Guarani squatters. Clashes on her property have emerged. "We cannot, as nonnative, be treated as second-class citizens," she said. Instead, we, too, should have the right to defend ourselves. Guarani leaders say they are also stymied in their claims by the legal process, involving anthropological studies and rulings by bureaucrats in Brasília for determining land ownership. Meanwhile, tensions smolder across Mato Grosso do Sul, and threats persist against the Guarani. A Guarani leader, Tonico Benites, 39, described one harrowing encounter in April. He said a gunman on a motorcycle stopped him and his wife on a deserted road and threatened to kill him because of his efforts to recover lands. A thunderstorm ended that encounter, said Mr. Benites, who still shakes when recounting it. "I told myself, "I'll scream until I'm killed; my wife will hear me, maybe someone else," " he said. They can eliminate me, but I won't go without a scream. Lis Horta Moriconi contributed reporting from Rio de Janeiro.