US calls for 'credible' probe into Myanmar atrocities
The diplomat met with leaders on Wednesday to discuss reports of human rights abuses against Rohingyas at the hands of Myanmar's security forces.
More than 600,000 Rohingya Muslims have fled to Bangladesh since August describing accounts of murder, rape and arson committed by Myanmar's army during a military crackdown. The onslaught has been described by the UN as a "textbook example of ethnic cleansing".
"We're deeply concerned by credible reports of widespread atrocities committed by Myanmar's security forces and by vigilantes who were unrestrained by the security forces during the recent violence in Rakhine state," Tillerson said in a joint news conference with Myanmar's leader, Aung San Suu Kyi.
"The recent serious allegations of abuses in Rakhine state demand a credible and impartial investigation and those who commit human rights abuses or violations must be held accountable," he added.
"In all my meetings, I have called on the Myanmar civilian government to lead a full and effective independent investigation and for the military to facilitate full access and cooperation."
Tillerson emphasised the military's duty to help Suu Kyi's government in meeting its commitment to ensuring the safety and security of all civilians in the Rakhine state.
An internal investigation conducted by the military was released earlier this week, clearing themselves over the reported Rohingya atrocities, and was described as 'white-washing' by human rights groups.
"Myanmar's response to this crisis is critical to determining the success of its transition to a more democratic society," Tillerson said.
"It's a responsibility of the government and its security forces to protect and respect the human rights of all persons within its borders and to hold accountable those who fail to do so."
In the past, Suu Kyi has defended the military operation, and authorities claim the security crackdown was in response to attacks by Rohingya militants on police posts.
The Rohingya have faced discrimination for decades in Buddhist-majority Myanmar where they are denied citizenship and denigrated as illegal 'Bengali' immigrants.