Canada's special envoy on the Rohingya crisis in Myanmar says it's hard to put the extent of the humanitarian crisis into words.

Bob Rae issued his interim report on Thursday night on the crisis that has seen hundreds of thousands of Rohingya Muslims flee Myanmar to neighbouring Bangladesh because of a crackdown by Myanmar security forces.

Rae's interim report said refugee camps are "deplorably overcrowded and pose a threat to human health and life itself."

Prime Minister Justin Trudeau appointed the former Ontario premier earlier this year to give him advice on the humanitarian crisis, which the United Nations has described as ethnic cleansing.

Seeing these words in print makes me realize how inadequate words are to express the extent of the damage and trauma. - Bob Rae in his interim report

Rae travelled to Bangladesh earlier this year to see the situation and has also met with a number of leaders, officials and non-governmental organizations in the region.

His interim report drew particular attention the plight of women, saying he heard detailed and graphic accounts from women who made it to Bangladesh about sexual violence and abuse at the hands of the Myanmar military.

Rae said those accounts included sexual violence as a weapon of war and there is clear evidence of sexual trauma among the women who survived.

"A focused effort to deal with this issue is required," the report said.

"Seeing these words in print makes me realize how inadequate words are to express the extent of the damage and trauma being suffered by women and girls among the Rohingya refugees."

Rae said the international community must get involved in addressing the issue and additional resources will be required.

"These allegations of crimes against humanity need to be addressed directly by the international community, and there is a need for post-traumatic measures to help those who survived this ordeal."

Rae returns in January

The United Nations Human Rights Council has appointed a fact-finding mission to examine the treatment of the Rohingya, but officials have not been allowed to visit Myanmar or interview officials in the country's government and military, Rae said.

The investigation into what happened must be "thorough and systematic" and must gather evidence and examine events over the past several years, the report said, adding that Canada must remain involved in this "important" international work.

The International aid group Doctors Without Borders said last week that it conducted a field survey that found at least 6,700 Rohingya Muslims were killed between August and September in the crackdown.

International rights groups blame the government and military for being unwilling to investigate possible wrongdoing by government officials and have urged Myanmar to accept the assistance of international investigators.

Myanmar's military said in a statement Monday that legal actions would be taken against the perpetrators.

Rae said he intends to return to Bangladesh in the New Year to continue his "challenging assignment" and have more talks with officials in Myanmar, Bangladesh and international organizations before completing his final report and issuing recommendations.