A North Korean man will be freed from Malaysian custody because of a lack of evidence connecting him to the fatal nerve agent attack on the estranged half-brother of North Korea's ruler.

Ri Jong-chol was held in police detention for almost two weeks following the assassination of Kim Jong-nam at Kuala Lumpur's bustling airport on February 13.

"He will be released. He is a free man. His remand expires and there is insufficient evidence to charge him," said Malaysian Attorney-General Mohamed Apandi Ali on Thursday.

Mohamed said Ri will be deported because he does not have valid travel documents."He will be deported tomorrow," he said.

In a major fallout from the assassination, Malaysia also announced on Thursday it was scrapping visa-free travel for North Koreans.

Who produced the VX poison that killed Kim Jong-nam?

Officials never said why they arrested Ri four days after Kim was attacked.

The attack was caught on grainy security camera footage that showed two women smearing something on Kim's face as he waited for a flight. Malaysian officials say the substance was VX nerve agent, a banned chemical weapon.

North Korea is widely speculated to be behind the killing. Experts say the oily poison was almost certainly produced in a sophisticated state weapons laboratory.

Pyongyang has denied the accusations and said it was "absurdity" to believe the chemical weapon VX was used in Kim's killing.

Kim was dead within an hour as the fast-acting poison coursed through his body, authorities say. No bystanders reported falling ill.

Deputy Prime Minister Ahmad Zahid Hamidi said Thursday the visa-free arrangement with North Korea will be scrapped from Monday because of national security. He also slammed the North Korean ambassador in Kuala Lumpur who accused Malaysia of "trying to conceal something" and "colluding with hostile forces".

"We don't want to make enemies, but if they had used Malaysia for their own agenda, they should not accuse Malaysia and tarnish our image on the international stage," Zahid said. "We will act firmly to guarantee the safety of our people. Don't ever use Malaysia as a base to do anything you like."

Malaysia to cancel visa-free entry for North Koreans

The two female suspects caught in the security footage were charged with murder in a Malaysian court Wednesday. They face the mandatory death sentence if convicted.

Both say they were duped into thinking they were taking part in a harmless prank.

Kim reportedly fell out of favour with his father, the late Kim Jong-il, in 2001 when he was caught trying to enter Japan on a false passport to visit Tokyo Disneyland.

He was not known to be seeking political power, but his position as eldest son of the family that has ruled North Korea since it was founded could have made him appear to be a danger to his half-brother Kim Jong-un.