Searchers have been trying to locate the six crew members missing following Sunday's explosion [Al Jazeera]

A South Korean cargo ship has been rocked by an explosion off the country's west coast, officials say.

The unexplained explosion tore apart the front of the ship and left the 4,198-ton vessel half-submerged, South Korean coast guard officials said on Sunday.

At least three people were reportedly killed, with several others missing,

Two of the bodies located later had serious external wounds, suggesting they had been killed by the explosion, Kim Dong-jin, a coast guard officer, told the Associated Press news agency.

Five crewmen were rescued and searchers were trying to locate six others who were reportedly missing, the coast guard said in a statement.

The explosion occurred relatively far from the tense sea border with North Korea, and the coast guard does not suspect the North was involved, Ko Jae-young, another coast guard officer, said.

North Korea is accused of torpedoing a South Korean warship in 2010, killing 46 sailors, though the North has denied involvement.

The cargo ship, which usually carried refined petroleum products and chemicals, was carrying 80 tons of bunker-C oil and 40 tons of diesel oil as its fuel when it exploded, the statement said.

Oil leakage was not immediately reported, it said.

Eleven members of the crew are from South Korea, and the other five are from Myanmar.