POPTÚN, Guatemala — The Guatemala military, once one of the most brutal and feared in Central America, is resurging to take on violent crime, forging closer ties with American troops and law enforcement even as worry over human rights abuses and corruption intensifies.

Those concerns deepened in recent weeks with the revelation of ties between former soldiers and drug gangs, and the fatal shooting of several indigenous demonstrators by soldiers on patrol with the police, an event critics of the militarized approach to policing seized on as an example of what can go wrong.

Allegations of corruption and killings by the military have also raised questions about the partnership with the American antidrug program here, just as the United States is reassessing its collaboration with security forces in neighboring Honduras after their role in several deadly episodes there.

“The army should take care of security of the country against attacks from a foreign power and never for citizen security,” said Francisco Dall’Anese, the former Costa Rica attorney general who now heads a United Nations commission investigating crime and corruption in Guatemala. He added, “When the military intervenes in conflicts of a civil nature, danger is increased without reaching solutions.”