Four more families of refugees and a cohort of single men have left immigration camps on Nauru to start new lives in the United States.

The group of 29, including eight children, who flew off the island nation today is the fifth group to depart Nauru under Australia's refugee resettlement deal with the US.

They included two Sri Lankan, one Rohingyan and one Afghan family and single men from Sri Lanka, Afghanistan, and Pakistan.

Since resettlements under the deal started in September, 139 refugees have left Nauru and 85 from Papua New Guinea's Manus Island.

However, the Refugee Action Coalition said it was remarkable there were no Iranian, Somali or Sudanese refugees among those who have left this year, despite Australian Border Force officials denying any particular nationalities were banned from resettling in the US.