Malaysian police have identified a senior official in the North Korean embassy as a suspect in the killing of Kim Jong-nam, and said another was linked to the North Korean state airline, Air Koryo.

Police chief Khalid Abu Bakar said on Wednesday that both suspects are still in Malaysia and have been called in for questioning, adding that the North Korean diplomat held the rank of second secretary at the embassy.

Kim Jong-nam, the estranged half-brother of North Korean leader Kim Jong-un, was killed at Kuala Lumpur International Airport last week while he was preparing to board a flight to Macau.

Khalid told a news conference that police "strongly believed" four other suspects who fled Malaysia on February 13, the day of the attack, had arrived in the North Korean capital of Pyongyang.

READ MORE: Kim Jong-nam's killing one week on - What we know

Abu Bakar also said that two women who are already in custody over the killing, one Indonesian and one Vietnamese, knew they were taking part in a poison attack, despite reports they believed it was a prank.

"Yes, of course, they knew," Abu Bakar said when asked by a reporter if the women knew they were carrying a toxic substance when they approached Kim Jong-nam.

"I think you have seen the video, right? The lady was moving away with her hands towards the bathroom. She was very aware that it was toxic and that she needed to wash her hands."

Indonesian police had said one of the suspects had been duped into believing she was taking part in a TV prank show.

Abu Bakar said that North Koreans placed the toxin on the hands of the two women.

READ MORE: Half-brother of Kim Jong-un 'killed' in Malaysia

He said the North Korean suspect who gave them the toxin is in custody and Malaysian authorities are seeking seven others, including two Khalid announced on Wednesday.

He said three suspects were believed to still be in Malaysia, including the embassy worker and the employee of state airline, Air Koryo.

Khalid referred to the victim, Kim Jong-nam, as Kim Chol, the name on his passport.