China urged calm and restraint yesterday after South Korea proposed the possible suspension of North Korea's seat at the United Nations to punish it for using chemical weapons to kill the half-brother of its leader.

Malaysian police have said two women smeared VX nerve agent, a chemical on a UN list of banned weapons of mass destruction, on Kim Jong-nam's face in an assault captured on security cameras in KL International Airport 2 on Feb 13.

US and South Korean officials believe Kim Jong-nam was the victim of an assassination orchestrated by North Korea.

North Korea said on Tuesday it "categorically rejects" what it called "fictitious and preposterous assumptions".

Speaking at the UN-backed Conference on Disarmament in Geneva on Tuesday, South Korean Foreign Minister Yun Byung-se said the use of chemical weapons was a "wake-up call" and the international community should act - including possibly suspending the isolated North's seat at the United Nations.

"What I need to say is that the situation at present on the Korean peninsula is complex and sensitive," Chinese Foreign Ministry spokesperson Geng Shuang said when asked whether North Korea should be suspended from the United Nations.

"In this situation, we hope all sides can maintain calm and exercise restraint and not do anything to irritate each other or that may raise regional tensions," Geng told a daily news briefing, without elaborating.

While China is North Korea's most important remaining international supporter, it has been angered by its repeated missile and nuclear tests and has supported tough UN sanctions.

China wants talks to resolve stand-off

However, China has pushed for talks to resolve the stand-off, and this week is playing host to a senior North Korean diplomat, Vice-Foreign Minister Ri Kil-song, the first such high-level visit since June last year.

In a brief statement, China's Foreign Ministry said Foreign Minister Wang Yi told Ri that China's consistent position is that it wants to consolidate the tradition of friendship between the two countries.

Wang said all parties should "iron out challenges" and work hard for the denuclearisation of the peninsula, the ministry added.

There was no mention in the statement of the death of Kim Jong-nam.

Under the Chemical Weapons Convention, the Organisation for the Prohibition of Chemical Weapons states parties can, "in cases of particular gravity", bring an issue to the attention of the UN Security Council and the UN General Assembly.

The UN Security Council can recommend to the 193-member General Assembly - likely through the adoption of a resolution - that a state be suspended or expelled. Such a move would need to be approved by a two-thirds majority of the General Assembly.

Kim Jong-nam had been living in exile, under Beijing's protection, in the Chinese territory of Macau, and had criticised the regime of his family and his half-brother, North Korean leader Kim Jong-un.

- Reuters