A refugee who raped a ten-year-old boy has claimed he did not know sexually assaulting the child was wrong as it was 'culturally acceptable' in his homeland.

Mufiz Rahaman told Sydney's Downing Centre Court raping children was not seen as morally wrong in his native Myanmar when he pleaded guilty to the aggravated sexual assault of a 10-year-old refugee on Wednesday, the Daily Telegraph reported.

The 20-year-old and his young victim are both stateless Rohingya Muslims - a group of people considered illegal immigrants from Bangladesh by the Buddhist-majority in Myanmar - who came to Australia to flee religious persecution.

The court heard Rahaman preyed on the young boy while he was living with a group of refugees, including his father, at a vacant RSL club in Lakemba, a suburb in Sydney's south west, on January 8, 2015.

According to documents tendered to the court, he crept into the child's bedroom - which he shared with his father - as he slept and took off the boy's underpants.

He then raped the boy….