U.S. Defense Secretary Chuck Hagel said China is "destabilizing" the South China Sea by pursuing territorial disputes with other nations and its actions are threatening the region’s long-term progress, while warning that the U.S. will "not look the other way" if international rules are ignored, according to media reports.

Beijing's recent deployment of a giant oil rig in a disputed portion of the South China Sea between the Paracel Islands and the Vietnamese coast, gave rise to tensions between China and Vietnam, which sparked anti-China rioting in Vietnam earlier this month. Taiwan, Brunei, the Philippines and Malaysia also claim parts of the South China Sea.

"In recent months, China has undertaken destabilizing, unilateral actions asserting its claims in the South China Sea," Hagel reportedly said while speaking at an international security conference in Singapore on Saturday, involving the U.S. and Southeast Asian countries.

Hagel also reportedly said: "All nations of the region, including China, have a choice: to unite and recommit to a stable regional order, or to walk away from that commitment and risk the peace and security that has benefited millions of people."

Japanese Defense Minister Itsunori Onodera reportedly said that Tokyo identifies an "increasingly severe regional security environment."

"It is unfortunate that there are security concerns in the East and South China Seas," he reportedly said. "Japan as well as all concerned parties must uphold the rule of law and never attempt to unilaterally change the status quo by force."

Hagel’s comments comes a day after Chinese President Xi Jinping vowed that his country will not increase tensions in the South China Sea but also said that China will react to provocations by other countries “in the necessary way,” the official Xinhua news agency reported Friday.

Xi also reportedly told Malaysia's Prime Minister Najib Razak that the situation in the South China Sea was "stable in general, but signs deserving our attention have also emerged.”

According to Xinhua, Xi said that China and Malaysia should "work together to strengthen dialogue and communication, advance maritime cooperation and joint development to maintain peace and stability on the South China Sea."