China's foreign ministry late on Sunday slammed what it claims were "irresponsible remarks" made by the US and Japan on the South China Sea and Taiwan at the Shangri-La Dialogue in Singapore.

But Prime Minister Malcolm Turnbull's tough words on China made at the same security conference went unmentioned by Beijing.

Foreign Ministry spokeswoman Hua Chunying said China had "indisputable sovereignty" over the Spratly Island, which China calls the Nansha Islands, where the US Navy recently made its first freedom of navigation patrol under the Trump presidency.

China respects freedom of navigation but "opposes certain country's show of force in the South China Sea under the pretext of navigation and overflight freedom, challenging and threatening China's sovereignty and security", she said.

Australia was expected to come under pressure from the United States on Monday during AUSMIN security talks with General Mattis and US Secretary of State Rex Tillerson to join the US freedom of navigation patrols in the South China Sea.

In the past, Australia has declined to do so. Instead Australia has continued to express its general support for freedom of navigation.

The likely request from the US to Australia could be one reason why Beijing did not include Australia in its criticism on Sunday, despite the direct language in Mr Turnbull's keynote speech.

General Mattis, Japan's defence minister Tomomi Inada and Australia's defence minister Marise Payne had issued a joint statement at the forum expressing strong opposition to the use of coercion in the South China Sea, and opposing "the use of disputed features for military purposes".

Ms Hua hit back saying China was within its sovereignty to build defence facilities on the islands and claimed it was exercising "self defence rights ... and it has nothing to do with 'militarization'."

She said the situation in the South China Sea has "calmed down and turned positive" after China and the Philippines had "reached consensus on properly managing the South China Sea issue including the arbitration case".

"In disregard of all these facts, certain countries outside the region, driven by ulterior motives, insist on making erroneous remarks and calling white black," she said.

The Hague ruled last year that China had no sovereignty over the islands, in a case brought to the international tribunal years earlier by the Philippines, but a change in government has seen the Philippines opt to negotiate with China.

China recently met with ASEAN countries and said it had reached agreement on a framework for a code of maritime conduct in the South China Sea.

Some ASEAN countries are reportedly concerned the code won't be legally binding, an issue addressed by the joint statement by the US, Australia and Japan at the Shangri-La forum.

In his speech, General Mattis also mentioned Taiwan for the first time since the forum started in 2002. He said the US department of defence was steadfastly committed to providing Taiwan's democratic government with the "defence articles necessary", as it was obliged to under US law.

The comments were the strongest show of support for Taiwan since Mr Trump broke decades of protocol and accepted a phone call from Taiwan president Tsai Ing-wen as president-elect.

Ms Hua said that China opposed the US "Taiwan Relations Act" and the US should "stop selling arms to Taiwan, stop all forms of official interaction with Taiwan and any attempt to elevate its relations with Taiwan".

Mr Turnbull's speech, in which he warned a "coercive China would find its neighbours resenting demands they cede their autonomy", attracted attention in Chinese media, and debate in Australia. Foreign policy analyst Hugh White wrote in the Australian Financial Review on Monday that Mr Turnbull had "threatened China with Cold War style containment".

Chinese newspaper The Global Times said it was "one of the most assertive comments from a Western leader on China".