Australia's foreign minister, Julie Bishop, says she has sought assurances from Nauru's government that due process and the rule of law is being upheld on the island.
Five opposition MPs have been expelled from parliament for more than a year, with three of them now facing criminal charges after a protest outside Parliament in June, while another has had his passport suspended.
There has also been widespread criticism of new laws that restrict freedom of expression and assembly, as well as restrictions on internet access and social media.
In a statement, Julie Bishop says she has conveyed Canberra's concerns about the situation to Nauru's president, Baron Waqa, and the Australian Government continues to closely monitor developments.
However, she says the issues are a domestic matter for Nauru.
Her comments follow those made by New Zealand's foreign minister, Murray McCully, who says he's deeply concerned about the situation and has sought a meeting with Nauru government representatives at a Pacific Islands Forum Ministers meeting in Sydney next week.