A plane carrying a military delegation from Guinea to attend an annual armed forces day in Liberia crashed Monday in the Liberian town of Charlesville, Monrovia said.

"There has been a plane crash in Charlesville at about five miles (eight kilometres) from the Roberts International Airport," said Liberian Information Minister Lewis Brown.

Authorities do not yet know if there were casualties, nor what kind of plane was involved or how many people were on board, said Brown, who was on his way to the scene.

"This plane was bringing the Guinean delegation from Conakry to Monrovia. This delegation was to attend the armed forces day in Liberia," he said.

Liberia holds an armed forces day each year to recognise its military, often inviting delegations from neighbouring countries, including Guinea, its neighbour to the north.

Roberts International, Liberia's main airport, is located about 65 kilometres southeast of Monrovia.

Much of the area where the plane went down is covered in deep forest.