The South Korean emergency helicopter carrying seven people crashed into the sea near the disputed Dokdo / Takeshima island group, with the fate of those on the plane unknown.

The accident happened last night, shortly after the helicopter took off from the disputed Dokdo / Takeshima island group to transport patients to the inland hospital. The crashed plane appears to be an EC-225 multipurpose helicopter, which has five rescue workers and two fishermen on board, according to South Korea's Yonhap news agency.

South Korea has deployed dozens of maritime police ships and many private fishing vessels to search for survivors. The Ministry of Defense also dispatches ships, aircraft and divers to assist in rescue operations. However, no victims were found.

South Korea controls Dokdo / Takeshima in the East China Sea, but Japan also claims sovereignty over the islands. South Korea claims it has freed the island group from Japanese rule since 1945, while Tokyo accuses Seoul of illegal occupation.

Dokdo / Takesshima Island group location Graphics: Economist.