Beijing should make Singapore "pay the price for seriously damaging China's interest", said a Chinese defence adviser days after a spat erupted between a Chinese newspaper and a Singapore envoy.

Professor Jin Yinan, a director at a defence university run by the People's Liberation Army, told state-owned China National Radio on Thursday that Singapore has actively pushed to make the South China Sea issue an international affair.

The Republic has provoked confrontations between China and the United States to show its relevance, he said.

"China's retaliation against Singapore is inevitable, not just in the public opinion sphere... We should take some actions, to strike back or impose sanctions, to show our displeasure," Prof Jin was quoted as saying.

His remarks followed an exchange of letters last week between Singapore Ambassador to China Stanley Loh and the Global Times over the words and actions of Singapore officials at a multilateral summit.

In a Sept 21 report, the Chinese newspaper had singled out Singapore for raising the South China Sea issue and the July arbitral tribunal ruling ata recent world summit.

Experts told The Sunday Times that Prof Jin's view reflects an increasing frustration among a certain growing quarter in China.

"Beijing accepts that Singapore can have different opinions, but it doesn't want to see Singapore rushing to the fore," said Sino-Asean expert Xu Liping from the Chinese Academy of Social Science, referring to the South China Sea issue.

Jinan University analyst Zhang Mingliang said this public spat has drawn an "unprecedented wave" of negative criticism against Singapore, especially among netizens. Yet, he views this as a superficialepisode that will blow over soon. "It's not likely to have any substantial impact on bilateral ties," he added.

Singapore's Defence Minister Ng Eng Hen yesterday reiterated a call to step up cooperation in the South China Sea at a maritime cooperation roundtable in Hawaii.

Referencing the Declaration on the Conduct of Parties (DOC), he said in his speech that "all claimant states and the overall situation in the South China Sea have fallen short of the hopes and standards set by the DOC".

The DOC is a key agreement to guide peaceful resolution of disputes and cooperative behaviour in the South China Sea signed by Asean and Chinese leaders in 2002. "We need to address this problem quickly before it escalates," he added.

In an interview yesterday, Dr Ng noted that the July arbitral tribunal ruling is legally binding under the United Nations Convention on the Law of the Sea. But other than legal claims, there are also practical concerns to deal with in this key waterway, such as accidents by non-military ships, he said.

He added: "For Singapore as a non-claimant state, our main interest is whether with or without the ruling, how do you make sure that the region is still stable and that you have mechanisms to prevent any escalations."