GENEVA/KUALA LUMPUR (Reuters) - South Korea called for "collective measures" to punish North Korea for using chemical weapons to kill the estranged half-brother of its leader Kim Jong Un, as Malaysia said on Tuesday it would charge two women with murder over the airport attack.
Police have said the women smeared VX nerve agent, a chemical on a United Nations list of banned weapons of mass destruction, on Kim Jong Nam's face in an assault captured on security cameras in the Malaysian capital's airport on Feb. 13.
U.S. and South Korean officials believe he was the victim of an assassination orchestrated by Pyongyang. North Korea said on Tuesday it "categorically rejects" what it called "fictitious and preposterous assumptions".
Speaking at the U.N.-backed Conference on Disarmament (CD) in Geneva on Tuesday, South Korea's 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.
"Many international media pointed out that North Korea's use of chemical weapons for the targeted killing in a third country sent a very clear message to the world," South Korea's Yun told the Geneva forum.
"Namely this impulsive, unpredictable, trigger-happy and brutal regime is ready and willing to strike anyone, anytime, anywhere."
North Korea called his comments "despicable and ill-natured".
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, Kim Jong Un.
Malaysian police arrested a Vietnamese woman, Doan Thi Huong, and an Indonesian, Siti Aishah, in the days after the attack.
Police are also holding one North Korean man and have identified seven other North Koreans wanted in connection with a case that reads like the plot to a spy movie.
Both women will be formally charged on Wednesday under section 302 of the penal code, which carries the death penalty, Malaysia's attorney general, Mohamed Apandi Ali, confirmed to Reuters in a text message.
VX is one of the deadliest chemical weapons ever created, far more potent than Sarin, the gas used in deadly chemical attacks in Syria in 2013 and in an attack on the Tokyo subway by a Japanese doomsday cult in 1995.
"Just a few grams of VX is sufficient for mass killing," Yun said.
"North Korea is reported to have not just grams but thousands of tonnes of chemical weapons, including VX, all over the country ... The recent assassination is a wake-up call to all of us to North Korea's chemical weapons capability and its intent to actually use them."
States could invoke the Chemical Weapons Convention as the use of such agents was in "flagrant violation of international law", Yun said. Malaysia is part of the 1993 pact prohibiting their production, transfer and use, but North Korea is not.
Once the Malaysian government releases the results of its investigation, the U.N. Security Council and state parties to the Chemical Weapons Convention should take up the case as a "high priority agenda", Yun said.
States that have ratified the chemical weapons ban could invoke the treaty and "take collective measures", he added.
"It could take the form of suspension of North Korea's rights and privileges as a U.N. member," he said.
His comment drew an angry response from North Korea.
"North Korea totally rejects the despicable, irresponsible, impertinent and illogical remarks made by South Korea," North Korean diplomat Ju Yong Choi told the same meeting in Geneva later on Tuesday.
"DPRK has never produced or stockpiled or used chemical weapons and our position is clear," he added, using the abbreviation for North Korea's official name, the Democratic People's Republic of Korea.
Security camera footage, which has been broadcast in the media, showed two women assaulting Kim Jong Nam in the departure hall of Kuala Lumpur International Airport. He died within 20 minutes.
Both of the women arrested have told diplomats from their countries that they had been paid to take part in what they believed was a prank for a reality television show.
Huong, the Vietnamese woman, was detained 48 hours after the murder in the same airport terminal where Kim Jong Nam was killed.
She is believed to be the woman wearing a white shirt emblazoned with the acronym "LOL", whose image was caught on security cameras while waiting for a taxi after the attack.
The Indonesian woman, Siti Aishah, was detained a day later.
Police have said the women knew what they were doing when they attacked Kim Jong Nam and were instructed to wash their hands afterwards.
Police said Aishah fell sick, vomiting repeatedly while in custody possibly as a side-effect of VX, though Indonesian embassy officials have subsequently said she was in good health.
Reporting by Stephanie Nebehay and Tom Miles in GENEVA, Joseph Sipalan and Angie Teo in KUALA LUMPUR and Zahra Matarani in JAKARTA; Writing by Alex Richardson; Editing by Robert Birsel and Mike Collett-White