BANGKOK — Myanmar’s military systematically planned a genocidal campaign to rid the country of Rohingya Muslims, according to a report released on Thursday by the rights-advocacy group Fortify Rights based on testimony from 254 survivors, officials and workers over a 21-month period.

The 162-page report says that the exodus of around 700,000 Rohingya Muslims to Bangladesh last year — after a campaign of mass slaughter, rape and village burnings in Rakhine State in Myanmar — was the culmination of months of meticulous planning by the security forces.

Fortify Rights names 22 military and police officers who it says were directly responsible for the campaign against the Rohingya and recommends that the United Nations Security Council refer them to the International Criminal Court.

“Genocide doesn’t happen spontaneously,” said Matthew Smith, co-founder of Fortify Rights. “Impunity for these crimes will pave the path for more violations and attacks in the future.”

Beginning in October 2016, Myanmar’s military and local officials methodically removed sharp tools that could be used for self-defense by the Rohingya, destroyed fences around Rohingya homes to make military raids easier, armed and trained ethnic Rakhine Buddhists, and shut off the spigot of international aid for the impoverished Rohingya community, the Fortify Rights report says.

Most of all, more troops were sent to northern Rakhine State, where the bulk of the largely stateless Rohingya once lived. Fortify Rights says that at least 27 Myanmar Army battalions, with up to 11,000 soldiers, and at least three combat police battalions, with around 900 personnel, participated in the bloodletting that began in late August and continued for weeks afterward.

United States officials have said that the violence amounted to a calculated campaign of ethnic cleansing, and one United Nations official described the anti-Rohingya campaign as bearing “the hallmarks of genocide.”

The Fortify Rights report suggests an alternate story line to the suggestion that the military-led atrocities, which were often abetted by ethnic Rakhine locals armed with swords, were solely a response to attacks by Rohingya militants on army and police posts on Aug. 25, 2017.

Myanmar’s military and civilian government have consistently described the crackdown as “clearance operations” against Muslim “terrorists.” Top military officers, including Senior Gen. Min Aung Hlaing, the army chief, have claimed that the military reacted with restraint following the deadly raids by the Arakan Rohinyga Salvation Army in October 2016 and August 2017.

Daw Aung San Suu Kyi, Myanmar’s de facto leader, in the capital, Naypyitaw, in 2016 with Senior Gen. Min Aung Hlaing. Credit Hein Htet/European Press photo Agency

“There is no genocide and ethnic cleansing in Myanmar,” said U Zaw Htay, a government spokesman. “Yes, there are human rights violations, and the government will take action against those who committed human rights violations.”

Beginning in October 2016, Myanmar’s military and local officials methodically removed sharp tools that could be used for self-defense by the Rohingya, destroyed fences around Rohingya homes to make military raids easier, armed and trained ethnic Rakhine Buddhists, and shut off the spigot of international aid for the impoverished Rohingya community, the Fortify Rights report says.

Mr. Zaw Htay said that the Myanmar government would be forming an “investigation team, which will include internationally well-respected persons to investigate the human rights violations in Rakhine.”

Several commissions, committees and investigative bodies have been formed in Myanmar to examine the Rakhine violence. But none have, so far, resulted in substantive shifts in policy or broad admissions of blame by the state.

“There are international organizations that accuse Myanmar with the terms ‘genocide’ and ‘ethnic cleansing’ without evidence,” Mr. Zaw Htay added, naming Fortify Rights among them. “If there is evidence of genocide, then they can inform the government and our government will investigate and take action.”

Fortify Rights has accused the international community of failing to adequately condemn the years of state repression of the Rohingya and, more specifically, the mounting abuses in the months preceding last year’s military-led campaign.

The list of Myanmar military officials whom Fortify Rights finds directly responsible for attacks on Rohingya Muslims include the commander in chief, Senior Gen. Min Aung Hlaing; his deputy, Vice Senior Gen. Soe Win; and the chief of general staff, Gen. Mya Tun Oo.

By Hannah Beech