Self-incriminating action surely? (Malaysia / North Korea)

Metro 23 Feb 2017:  QUOTE Two women suspected of killing the half-brother of North Korea’s leader in Malaysia were trained to coat their hands with toxic chemicals then wipe them on his face, a police chief said yesterday.  They had practised the attack at two Kuala Lumpur shopping centres before targeting Kim Jong-nam at the city’s airport last week claimed Khalid Abu Bakar.  He said CCTV showed them keeping their hands away from their bodies after the fatal poisoning, then going to the toilets to wash.  North Korea — whose ruler Kim Jong-un is suspected of ordering the hit on his sibling — ridiculed the police claims.  It demanded the immediate release of the two ‘innocent women’, Doah Thi Huong, 28, from Vietnam and Siti Aisyah, 25, from Indonesia.  UNQUOTE

I can understand the "ridiculed the police claims" bit (an act of immediate self defence when accused).  But why should North Korea demand the immediate release of the two suspects when they aren't even N.Korean citizens?  Also, how did they come to the conclusion that they are innocent?  Finally, they're not even saying the women should be released; they are DEMANDING their IMMEDIATE release.  Self-incriminating surely?  

(Malaysia / North Korea, 2017)