Initial reports indicate there were 10 people on the plane and none of them survived, Voice of America reported.
Guinean officials said the crash occurred in Charlesville, about 28 miles southeast of the Liberian capital of Monrovia.
The Guinean delegation, which included army Gen. Kelefa Diallo, was traveling to Monrovia to attend Liberia's annual armed forces day, VOA said.
Liberian President Ellen Johnson Sirleaf declared Tuesday as a day of mourning.
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