The United States has increased monitoring of two Chinese polar research ships that regularly visit Australian ports.

The vessels, Xue Long and Xue Long 2, have been travelling to and from Antarctica through Australian facilities.

US authorities say they are tracking the ships to ensure activities comply with international law and to respond to any potential risks.

The Australian government has rejected a Freedom of Information request about the ships’ port access, citing national security concerns.

Security analysts say Australia should carefully monitor the vessels and their capabilities while avoiding unnecessary restrictions.

China says the ships are used for scientific research missions through the Polar Research Institute of China.

The issue has renewed debate over maritime security and China’s growing presence in polar regions.