A plane carrying officials of Equatorial Guinea's ruling party crashed at sea Wednesday, airport sources said, without stating whether there were any casualties.

The defence ministry aircraft, an Antonov-24, was carrying members of the ruling party to Annobon island to open an electoral campaign there on Friday, but it plunged into the sea while trying to land, the sources said.

Annobon is a remote island about 700 kilometres (435 miles) southwest of the tropical African country's capital Malabo, itself on an island, Bioko. But the plane had flown from the economic capital, Bata, on continental Africa.