New Zealand Minister of Defence Gerry Brownlee. Photo: File

China rebuked New Zealand's defence minister at a forum in Beijing on Tuesday, criticising his stance on tensions in the South China Sea, saying countries "not involved" should not interfere.

China claims almost the entire South China Sea, through which about $5 trillion worth of trade passes each year. Brunei, Malaysia, the Philippines, Taiwan and Vietnam also have claims to parts of the sea.

An international tribunal in the Hague ruled in July that China had no historic title over the waters and had breached the Philippines' sovereign rights there. That decision infuriated Beijing, which dismissed the court's authority.

We "hope that countries who are not involved in the disputes respect the countries who are having the disputes to ... work among themselves," Fu Ying, chairwoman of China's foreign affairs committee for parliament, said at the Xiangshan Forum, which China styles as its answer to the annual Shangri-La Dialogue security forum in Singapore.

"Outside involvement, I think the developments have shown, interferences, can only complicate the differences and sometimes even add to the tension," Fu, a former deputy foreign minister, said.

Fu, who was chairing the session, made her comments immediately after New Zealand Defence Minister Gerry Brownlee spoke at the start of the forum.

"We oppose actions that undermine peace and erode trust and would like to see all parties actively take steps to reduce those tensions," Brownlee said earlier.

"As a small maritime trading nation, international law and, in particular, the United Nations convention on the law of the sea, is important for New Zealand. We support the arbitral process and believe that countries have the right to seek that international resolution," he said.

This isn't the first time China has clashed with New Zealand over the territorial dispute.

In February, New Zealand urged Chinese restraint after Beijing's apparent deployment of an advanced missile system on a South China Sea island, while Beijing said New Zealand's proposal was "unconstructive".

Brownlee on Tuesday honed in on the issue of China's building of artificial islands in the territory, including new airstrips, which has rattled nerves around the region.

"A particular cause of... heightened tension has been the reclamation and construction activity and deployment of military assets in disputed areas," he said.

China says much of the building and reclamation work it has been doing in the South China Sea is to benefit the international community, including for civilian maritime navigation.

After Fu's response, Brownlee told Reuters on the sidelines of the forum that it was reasonable for New Zealand to express its concerns, which represent smaller countries as well, as all parties are able to have a say.

A Malaysian general told Reuters on the sidelines of the forum that China has exercised restraint over the dispute, and there has been no increase in Chinese military activity in the parts of the South China Sea which Malaysia claims.

"In fact we are establishing military cooperation with China to build up confidence so that we understand one another better," said Malaysia Armed Forces chief Zulkefli Mohd Zin.