A plane carrying a military delegation from Guinea crashed Monday in the Liberian town of Charlesville, killing the army chief of staff and 10 other people, officials said.

"The accident claimed the lives of the six members of the delegation led by General Souleymane Kelefa Diallo, chief of staff of the army, and the five members of the crew," Guinea's defence minister Abdoul Kabele Camara said in a statement.

Camara declared three days of national mourning starting Monday, with flags flying at half-mast.

Liberian President Ellen Johnson Sirleaf also declared a day of mourning for the victims on Tuesday.

"May all of us pray for the souls of the Guineans who died in the crash," she said on national television.

The plane was carrying the delegation to attend an armed forces day in Liberia, which holds ceremonies each year to recognise its military and often invites officers from neighbouring countries, including Guinea.

Emergency workers and police were dispatched to the crash site, about eight kilometres (five miles) from Liberia's only international airport.

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

The airport, Roberts International, is located about 65 kilometres southeast of the capital Monrovia.

Liberian officials were due to brief the press at the airport later in the day.

Guinean President Alpha Conde named Camara's deputy General Namory Traore as interim chief of staff.