Five people went missing on Sunday after their fishing boat sank off the coast of South Korea's southern port city of Busan, local media reported.

The accident took place at about 07:00 a.m. local time some 70 km off the coast of Busan, when the ship was operating in waters east of the port city, local authorities said.

All 25 fishermen on aboard the 129-ton boat fell into water, and 20 of them were later rescued by three ships from the same fleet operating nearby, while five, including three South Koreans and two Indonesians, went missing.

Witnesses were quoted as saying that the boat likely sank due to bad weather, but an investigation is still underway to determine the exact cause of the accident.

Local authorities has sent rescue helicopter and three coast guard vessels to search for the area for the missing people.