"We will process them in a way which doesn't involve entry into mainland Australia"
Kevin Andrews, Australian immigration minister
Andrews said the decision to turn away the latest batch of asylum seekers showed that the government was "committed to a strong border protection policy".
"[We] are also committed to sending the strongest possible message of deterrence to people who would engage in the dangerous and unlawful activity of people smuggling," he said.
"Our message to them and anyone else who would consider doing this is that we will process them in a way which doesn't involve entry into mainland Australia."
Earlier this month, Australia charged two Indonesian men with smuggling in the Sri Lankans.
Australia pays Nauru, a tiny and impoverished nation, to keep the refugees in detention.
The Nauru system became the focus of global attention in 2001 when a boatload of Afghan refugees was offloaded there.
Last September, Australia sent seven Myanmar asylum seekers to Nauru and reactivated the center after its last occupant, an Iraqi, sought medical treatment in Australia.
Refugee rights groups said sending the Sri Lankan group to Nauru would prohibit them from applying for protection in Australia.
Migration continues to be a major factor in shaping Australia's society and economy, is a politically-sensitive issue, with the government maintaining a tough stance on unauthorised arrivals.
Australia has proposed a citizenship test requiring new immigrants to pass an internet-based English language test and show a basic knowledge of the country.
About 99 per cent of Australia's population are of European or Asian descent.