US Defence Secretary Chuck Hagel has critised China’s “destabilising actions” in the South China Sea.

“In recent months, China has undertaken destabilising, unilateral actions asserting its claims on the South China Sea,” Chuck Hagel said at an international security conference.

“The United States will not look the other way when fundamental principles of the international order are being challenged,” continued Hagel.

The Pentagon chief’s comments come at a time of deep tension between China and Vietnam over Beijing’s decision to move a huge oil rig into disputed waters.

The move enraged Vietnam and sparked anti-China protests and riots.

China claims almost the entire South China Sea, potentially rich in oil and gas deposits.

Vietnam and Philippines also have claims on the area, as well as Brunei, Malaysia, and Taiwan.

Meanwhile, US ally Japan is pushing for a greater role in regional security. Japanese Prime Minister Shinzo Abe said he would offer his utmost support to Asian countries.

Many welcome that message, despite memories of Japan’s wartime aggression, because of China’s increasing assertiveness.