BORYEONG/TAEAN -- Three South Koreans were killed and 19 others were injured after their fishing boat collided with a bridge pier on the country's west coast earlier Saturday, the Korea Coast Guard said.

The accident occurred at around 5:41 a.m. when the 9.77-ton boat carrying 21 recreational fishermen and a skipper collided with one of the piers of a bridge connecting Anmyeon Island and Wonsan Island.

Three out of the four men found unconscious by the Coast Guard were pronounced dead at hospitals, while the fourth remained unconscious and in critical condition, said Lee Sung-il, a Coast Guard spokesman in the western coastal county of Taean.

Lee said 19 other men, including a 42-year-old skipper identified only by his family name Woo, are being treated at nearby hospitals for serious and minor injuries such as broken bones.

The Coast Guard plans to question the skipper as soon as he is released from the hospital on charges of professional negligence resulting in death, Lee said.

Lee said the skipper is believed to have failed to see a bridge pier due to darkness as his boat was traveling at between 15 and 18 nautical miles (27 and 33 kilometers) per hour.

There were no apparent issues with safety or weather conditions.

The boat was built to carry up to 22 people and the skipper was not drunk. The weather was relatively fair, with not much fog and waves measuring 1 meter in height.

But some have raised views that the fishing boat could have sped up to find a better spot for fishing, highlighting the need to regulate recreational fishing hours to after sunrise and before sunset for heightened safety.

Currently, fishing boats are allowed to leave the port after 4 a.m. and arrive before 8 p.m.

Most of the people on board were known to have come to Boryeong in groups for weekend fishing trips after reserving seats in advance online.

All passengers were wearing life jackets when they were rescued. (Yonhap)