Nineteen North Korean refugees, detained at a Myanmar border town early this month, have been released and sent to neighbouring Thailand, a government official said on Wednesday.

The group, which included 15 women and a young boy and had faced up to three years in prison for illegal entry, were sent to the border town of Tachileck, where they crossed into Thailand, said the official who declined to be named.

Hundreds of North Koreans flee the hermit state every year, usually crossing into China and then on to a third country on their way to eventual asylum in South Korea, rights groups say.

Many end up in Thailand, packing detention facilities. South Korea grants asylum to the North Koreans at a slower rate than they have been arriving, creating a bottleneck that has strained ties between Seoul and Bangkok.

A South Korean diplomat in Yangon confirmed the group were in Thailand and "will be allowed to go to South Korea".

The military-ruled former Burma severed its ties with North Korea in 1983 after a major bomb attack in Yangon, allegedly plotted by Pyongyang, against former South Korean President Chun Doo Hwan while he was on a state visit.

Seventeen South Korean officials in Chun's delegation, including cabinet ministers, were killed in the bomb attack at the Martyrs Mausoleum in Yangon.

Since restoring diplomatic ties in 2007, Myanmar and North Korea have hosted top-level visits by officials from the world's two most isolated countries.