A Chinese official dealing with Taiwan relations has said the two governments have a common responsibility to defend Chinese territorial claims in the South China Sea.

Yang Yi, a spokesman for China's Taiwan Affairs Office, said at a news conference in Beijing Wednesday that Chinese on both sides of the Taiwan Strait are obliged to defend Chinese sovereignty in the strategic waterway.

China and Taiwan have been bitter rivals for decades, with both claiming sovereignty over all of China. But relations have improved in recent years.

Yang also reiterated Beijing's claim that Chinese sovereignty over South China Sea islands and their surrounding waters is “indisputable.”

Both Vietnam and the Philippines have complained of aggressive Chinese action in areas near the disputed Spratly islands which the two countries claim as parts of their exclusive economic zones. The United States says a mutual defense treaty it signed with the Philippines in the 1950s extends to the dispute.

The Spratlys, a chain of shoals and islands which are believed to contain important oil and gas reserves, are claimed in whole or part by China, Taiwan, Vietnam, the Philippines, Malaysia and Brunei. China and Taiwan both base their claims in part on the same centuries-old Chinese map.

A Malaysian newspaper Tuesday quoted that nation's fleet commander saying Malaysia's navy is on standby around the clock to defend the country's interests in the area.

The eastern Malaysia-based Daily Express quoted Vice Admiral Wira Jamil Osman saying the navy is “closely monitoring” the disputes between China and other countries in the region. He said his forces will focus on safeguarding Malaysia's exclusive economic zone and some areas that overlap other countries' waters.

China and Vietnam also have conflicting claims to another South China Sea island chain, the Paracels.