South Korea has deported two North Korean fishermen after it was revealed they had killed 16 other crew members on their boat and then fled to South Korean waters.

Key points: 19 people were aboard the fishing boat when it left a North Korean port

19 people were aboard the fishing boat when it left a North Korean port A trio killed 16 colleagues, but one was arrested near a home port

A trio killed 16 colleagues, but one was arrested near a home port The remaining duo fled to South Korea seeking permanent residency

It is the first time that South Korea has deported any North Korean national who has come to South Korea since the end of the 1950–53 Korean War, according to Seoul's Unification Ministry, which deals with North Korean affairs.

The two North Koreans, both men in their 20s, were captured on Thursday (local time) in their boat in waters south-east of the Koreas last Saturday, according to the ministry.

It said a South Korean investigation later found the two had killed 16 colleagues, including the captain.

South Korea has a policy of accepting North Koreans who want to resettle in the South to avoid political oppressions and economic poverty at home.

Ministry spokesperson Lee Sang-min said South Korea decided to expel the two fishermen to North Korea because they were "heinous criminals".

He added that they could not be recognised as refugees under international laws.

Mr Lee said the two were sent back over land.

Fisherman accused boat captain of abuse

The trio accused of murder, not pictured, said the boat's captain was abusive. ( Flickr: Roman Harak )

According to the South Korean investigation, 19 people were aboard the squid fishing boat when it left the North's Kimchaek port on its east coast in August.

While fishing in waters near Russia and elsewhere, the two men collaborated with another crew member and killed the captain, who they said had abused them.

The trio later killed 15 other fishermen on the boat to cover up their action.

The three went back to Kimchaek port with the intention of moving to another region of North Korea.

But the third fisherman was arrested near the port, and the two fled North Korea using the same boat, the Unification Ministry said, citing the Government investigation.

When their boat sailed across the sea border last week, they were chased by a South Korean navy ship which fired warning shots at them.

After two days, the two were captured by the South Korean navy on Saturday.

Seoul says fisherman only wanted to avoid arrest

The two men were sent back home via the two Koreas' militarised land border. ( Reuters: Kim Hong-Ji )

The fishermen later told investigators they wanted to resettle in South Korea, but South Korean authorities determined they only wanted to avoid North Korean arrest and on Tuesday informed North Korea of their planned deportation, the ministry said.

Observers say the men are likely to receive heavy punishment in North Korea, including possible execution.

Some South Korean media questioned why the South Korean government made the deportation decision so early and whether it should have allowed the North Koreans to go through a South Korean judicial process first.

North Korean fishing boats have occasionally drifted into South Korean waters, and South Korea has usually accepted those who chose to resettle and repatriated others who wished to return home.

About 32,000 North Koreans have fled to the South since the end of the Korean War, primarily via China.

North Korean defectors are a sore point in relations between the two Koreas, with the North often claiming its citizens are held against their will in the South.

AP