Hong Kong — The U.S. Treasury Department on Friday imposed sanctions on three Myanmar military commanders and a border guard police commander, along with two entire military units, for their involvement in “ethnic cleansing” against Rohingya Muslims in Rakhine state.

It was the firmest U.S. action yet against the Myanmar military since it launched a brutal campaign against the minority group almost a year ago.

The move comes as the U.S. State Department readies a comprehensive report on atrocities in Rakhine state last August. The study could include findings on whether the military committed crimes against humanity or genocide against the Rohingya.

Human rights groups and experts have accused the military in Myanmar, also known as Burma, of waging a premeditated campaign against the Rohingya, disputing its explanation that it was merely responding to militant attacks on police posts. The army’s weekslong clearance operation in Rakhine state resulted in allegations of rape, indiscriminate killing and the torching of Rohingya homes.

The three Myanmar military commanders, Aung Kyaw Zaw, Khin Maung Soe and Khin Hlaing, and the border guard police commander, San Lwin, were sanctioned for their roles in leading campaigns against ethnic minority communities, the Treasury Department said in a news release. In addition to the campaign in Rakhine state, the military has “used many of the same tactics against a number of other ethnic and religious minority groups,” the department said, citing “extrajudicial killings, enforced disappearances, arbitrary arrests and torture against civilians.” Khin Hlaing was specifically sanctioned for his role in Shan state, in the country’s north, against ethnic Kachin and Chinese minorities.

The Treasury Department also sanctioned two entire military units — the 99th and 33rd light infantry divisions — in a rare move. Both units were designated for “engaging in serious human rights abuse,” the department said. Soldiers of the 33rd Light Infantry Division participated in last August’s campaign against the Rohingya and were accused of firing on fleeing villagers and raping women.

“Treasury is sanctioning units and leaders overseeing this horrific behavior as part of a broader U.S. government strategy to hold accountable those responsible for such wide-scale human suffering,” said Sigal Mandelker, treasury undersecretary for terrorism and financial intelligence. “The U.S. government is committed to ensuring that Burmese military units and leaders reckon with and put a stop to these brutal acts,” he added.

Several people familiar with the matter, who were not authorized to speak publicly, said the Treasury Department for months has had the names of Myanmar military commanders responsible for actions against the Rohingya. But the United States has been slower than other Western nations to respond to the atrocities while it determines the most appropriate foreign policy response.

Washington has been weighing the risk that sanctions or tougher actions against Myanmar would push the country closer to China, its neighbor to the north. The military’s actions against the Rohingya have boosted its popularity within the country, and Myanmar’s de facto civilian leader, Aung San Suu Kyi, has not spoken out strongly against the atrocities.

Canada and the European Union in June sanctioned seven Myanmar military and police leaders over similar accusations. Stronger action against Myanmar from Congress, meanwhile, has stalled as Senate Majority Leader Mitch McConnell, R-Ky., blocks any punitive action that could be perceived as directed toward Suu Kyi.