In a statement, Immigration Minister Scott Morrison says the government is not breaking any domestic or international laws.
"The government is taking the steps necessary to protect our borders consistent with our domestic laws and international obligations."
The UN refugee agency has warned that Australia could be breaking international law, amid reports that it pushed back to Indonesia boats carrying asylum-seekers.
Adrian Edwards, spokesman for the UN high commissioner for refugees, said on Friday that the agency wanted an explanation after the reports that the Australian navy forced boats back, as well as plans to buy more vessels to bolster such operations.
"UNHCR would be concerned by any policy or practice that involved pushing asylum-seeker boats back at sea without a proper consideration of individual needs for protection," Edwards told reporters, saying it was still seeking details from the government.
"Any such approach would raise significant issues and potentially place Australia in breach of its obligations under the 1951 Refugee Convention and other international law obligations."
Indonesia says Australia has turned back at least one boat carrying asylum-seekers to its shores, although The Australian reported that as many as five have been secretly returned.
"As past experience has shown, such practices are operationally difficult and potentially dangerous for all concerned," Edwards said.
On Friday, Abbott likened the fight against people-smugglers to war. The government has declined to reveal details of the boat incidents.
It has also refused to confirm or deny that it is planning to buy 16 hard-hulled lifeboats to ferry asylum-seekers to Indonesia.
Over the past decade, UNHCR has repeatedly crossed swords with Australian governments of all political stripes, including over the policy of sending arrivals to Papua New Guinea and Nauru pending asylum hearings.