North Korea has issued an informal apology to Vietnam for involving one of its citizens in the assassination of Kim Jong-un’s estranged half-brother in Malaysia, South Korean press reports have claimed.

The reports, which cannot be independently verified, cite a senior South Korean government official as saying that North Korea “belatedly apologised” for the alleged recruitment of a Vietnamese woman, Doan Thi Huong, by the son of a former ambassador.

Ms Huong, 29, and Indonesian woman Siti Aisyah, 25 are currently standing trial in Kuala Lumpur for the murder of Kim Jong-nam, after they smeared lethal VX nerve agent on his face at the international airport in February 2017. Both women, who face the death penalty if convicted, are pleading not guilty.

"The Vietnamese government and public were outraged by the involvement of a Vietnamese citizen in the assassination of Kim Jong-nam and bilateral relations chilled," the official said, in comments reported by the Chosun Ilbo.

"Vietnam demanded an official apology from North Korea and threatened to sever diplomatic ties."