NAM DINH, VIETNAM (Reuters) - A Vietnamese man said on Sunday (Feb 19) he believes his sister is one of the suspects arrested in Malaysia in connection with the murder of the half-brother of North Korean leader Kim Jong Un.

Kim Jong Nam was assaulted at Kuala Lumpur International Airport with what was thought to be a fast-acting poison. Malaysian police have said that among those arrested was a woman with a Vietnamese travel document.

Vietnamese authorities have said only that they are investigating and are in touch with Malaysia.

Joseph Doan confirmed that his sister's name was Doan Thi Huong and that she was born in 1988 in Nam Dinh province, southeast of the capital Hanoi.

Those details are the same as those released by Malaysian police.

"We only hear on the internet and everyone else hears on the internet but judging from the picture it looks like her. I can't be a 100 per cent certain because we haven't met her yet," he said in Nam Dinh.

The rice farmer said his sister appeared to be the woman whose image was captured in a grainy airport CCTV image wearing a white shirt with the acronym 'LOL' on it. He said Vietnamese authorities had been in touch and had been supportive.

Doan said his sister had left home when she was 18 and only came home occasionally and without letting anyone know when she would be back. "Whenever she comes home I can only tell her to study and work hard," he said.

South Korean and US officials have said Kim Jong Nam was assassinated by North Korean agents.

Malaysian police said on Sunday that four North Korean suspects in the murder fled Malaysia on the day of the killing.

Malaysian police arrested a North Korean man on Friday in connection to the murder, while a Vietnamese woman and an Indonesian woman have also been arrested. A Malaysian man is being detained to facilitate the investigation.