A South Korean tanker capsized off an island in southwestern Japan early Wednesday, and the coast guard said it had rescued four crew members and was still searching for seven who were missing.

The coast guard said it received a distress call from the Keoyoung Sun chemical tanker, saying that it was tilting while taking refuge near Japan's Mutsure Island due to rough weather.

The island is just off the southwestern end of Japan's Honshu main island, about 1,000 kilometers (620 miles) from Tokyo.

The ship later completely capsized, the coast guard said.

Footage on NHK television showed the ship completely upside down, a rough sea washing over its red underside.

The conditions of the rescued crew members were immediately not known.

NHK television reported the crew included a Chinese national, two South Koreans and eight Indonesians.

No other details, including how the ship capsized, were immediately known.