Five asylum seekers have accused Australia's navy of abuse, claiming they were kicked, handcuffed, racially abused and thrown out of the country.
A wooden boat containing 45 refuge seekers from Africa and the Middle East landed in Darwin, Australia, on New Year's day, Reuters reports.
Within one hour, military personnel allegedly forced the asylum seekers back onto their boat and towed it out to sea, heading for Indonesia.
According to the account of Yousif Ibrahim Fasher, an English-speaker from Sudan's Darfur region, men who resisted were picked up by their arms and legs and dumped in the boat. Fasher said he saw military personnel kick and use zip ties to handcuff one man who tried to flee.
"We told them: 'that direction, we lost people.' We told them everything. They said: 'No, you go back to the boat'," Fasher said.
"We refused, and then they used force."
Some of the guards called asylum seekers "monkeys" and told them they were not wanted in Australia, Fasher said.
Guards imposed strict discipline on the boat. Food and water were insufficient and some requests for medical help went unheeded, the asylum seekers claimed.
The Australians allowed only one visit to the toilet per day for men, and only night visits for women.
"I remember they used to stop us going to the bathroom. Forbidden to stand, forbidden to speak, forbidden to raise your voice," said Bakil Abdul Hamid, a 28-year-old Yemeni.
Hamid said his brother Mohammad was one of four people who were swept to their deaths on 1 January.
Immigration and border protection minister Scott Morrison said in a statement he did not give "credibility to malicious and unfounded slurs".
"I know and trust that our Navy and Customs and Border Protection Service act in accordance with their training and lawful orders and would only use force where necessary," Morrison said.
The UN refugee agency has warned that Australia could be breaking its obligations under the UN Refugee Convention by failing to hear asylum seekers' claims.
Australia's Human Rights Commission has already opened an inquiry into the alleged detention of more than 1,000 asylum-seeking children in immigration facilities under punitive government policies.
The pacific detention policy sees mandatory detention of all persons entering the country without a valid visa. Amnesty International severely criticised the laws as "[they] sacrifice the protection of refugees in favour of deterrence."
Australia is also believed to have repeatedly forced asylum seekers approaching the coasts to go back to Indonesia.
According to Human Rights Watch: "Australia again seeks to shunt desperate boat people to remote camps, perhaps for years, to punish them for arriving uninvited by sea."