Amnesty International (AI) has released a report on Monday saying the alleged attacks against the Rohingya Muslim minority by the Myanmar army may be considered crimes against humanity.
The report came on the day the Association of Southeast Asian Nations' foreign ministers were to meet in Yangon to address the ongoing Rohingya crisis in the western Rakhine state, Efe news reported.
Amnesty said Myanmar soldiers were responsible for executions and rapes in a campaign of violence against Rohingyas in Maungdaw district, north of Rakhine, flouting international law.
Neighboring Bangladesh was pushing back thousands of refugees as the crisis continued, it said.
Following interviews with Rohingyas in Myanmar and Bangladesh and analysis of satellite images, the London-based NGO accused Myanmar military of shooting Rohingya civilians and burning their houses.
"The deplorable actions of the military were part of a widespread and systematic attack on a civilian population and may amount to crimes against humanity," said Rafendi Djamin, AI's Southeast Asia director.
Djamin said the de facto leader of the Myanmar government, the Nobel Peace Prize Laureate Aung San Suu Kyi, has "failed to live up to both her political and moral responsibility".
"She has failed to try to stop and condemn what is unfolding in Rakhine State," Djamin added.
The Myanmar army launched a military operation in Maungdaw following an armed assault, blamed on Rohingya insurgents, on three border police posts on October 9, which left nine officers dead.
Independent observers and humanitarian aid was blocked from the area and more than 30,000 people, most of them Rohingya, were forced to flee. At least 27,000 fled to Bangladesh, according to the UN.
Amnesty said the Myanmar army has raped, shot and killed men, women and children, fired on villagers from helicopters, and burned down hundreds of houses.
Fatimah, a 32-year-old Rohingya woman who fled to Bangladesh, told Amnesty that soldiers raped her in a rice field near her village.
"Three military officers raped me. I don't remember what happened next because I fell unconscious. I woke up early the next morning. I could not get up so I crawled across the paddy field," she said.
Amnesty said the Rohingya fleeing the soldiers were forced into hiding in camps or in the jungle, living in miserable conditions.
It urged Bangladesh to provide humanitarian assistance to refugees.
Rakhine is home to more than one million Rohingya, a community not recognised as citizens in Myanmar and often shunned as Bangladeshi immigrants.
Around 120,000 of them live severely restricted lives in 67 camps since the outbreak of sectarian violence in 2012, when at least 160 people were left dead.
Bangladesh, for its part, also considers the Rohingyas as foreigners.