Four people were killed and two were missing after six fishing boats capsized early Tuesday off Nagasaki Prefecture as a low pressure system brought strong winds and heavy rain to the region, the Japan Coast Guard said.
Five fishing boats capsized off Tsushima Island, throwing eight crew members into the sea.
Two of the boats requested help at around 3:40 a.m., the Coast Guard said.
Elsewhere, a squid-fishing boat capsized off the coast of Shimonoseki, Yamaguchi Prefecture, at around 6:40 a.m., leaving one of two crew members missing.
Coast Guard patrol vessels were searching the area for the missing individual.
The atmosphere around the Tsushima Strait was unstable as southerly warm, moist air seeped into a low pressure system, according to the Japan Meteorological Agency.