Thirteen people were killed and two were missing after a fishing boat collided with a tanker off South Korea's west coast and capsized early today, the country's coastguard has said.

The Seonchang-1 fishing boat was carrying 20 passengers on a fishing tour as well as two sailors when it crashed with the 336-tonne fuel tanker at around 6am local time at sea near the port city of Incheon.

A number of people were found dead and others died after being sent to hospitals.

Seven others were being treated at hospitals while two - including the captain of the boat - remained missing, according to the coastguard.

No casualties or injuries were reported among those on board the tanker.

TV footage showed the fishing boat sinking beneath churning waves while rescue divers searched around the deck, part of which was still visible above the water.

All of the passengers were wearing life jackets but many appeared to have suffered hypothermia, Seoul's Yonhap news agency said.

Deadly accidents involving fishing tour boats often make headlines in South Korea.

This incident was the worst since September 2015 when 15 died after a fishing tour boat capsized near the southern resort island of Jeju.