
"The Myanmar military has targeted Rohingya civilians in a callous and systematic campaign of violence," Rafendi Djamin, Amnesty International's director for South-east Asia and the Pacific, said in a statement.
"The deplorable actions of the military could be part of a widespread and systematic attack on a civilian population and may amount to crimes against humanity."
Attacks on security forces in northern Rakhine state in October prompted a sweeping crackdown on the persecuted population and the army is accused of killing and raping civilians as well as burning down their homes.
State Counsellor Aung San Suu Kyi was Monday hosting informal talks with Asean foreign ministers in the commercial capital of Yangon to discuss the crisis.
Tens of thousands of Rohingya have fled to Bangladesh following the violence.
A 32-year-old Rohingya woman named Fatima told the rights group three soldiers raped her in a paddy field.
"I don't remember what happened next because I fell unconscious," she said. "I woke up early the next morning. I could not get up so I crawled across the paddy field."
The government denies the allegations, defending the military's actions as "clearance operations" to root out Rohingya militants.
Spokesman Zaw Htay could not immediately be reached for comment.