Twenty-four U.N. staff and others were killed in a helicopter that crashed Tuesday in Sierra Leone, the United Nations announced. The helicopter, leased by the U.N. peacekeeping mission in the West African country, was on an operational flight in the western part of the country. U.N. spokeswoman Marie Okabe said there were no survivors "in this tragic incident." Three Russian pilots were among the dead, she added. The helicopter was a Russian Mi-8MTV-1 from the UTair company, which has been involved in U.N. peacekeeping operations from East Timor to Iraq, has been used by the United Nations since the collapse of the Soviet Union. The helicopter took off from the Sierra Leone capital of Freetown but never arrived at its destination in the western city of Kailahun, U.N. sources said. Okabe said it crashed into a hillside in the jungle. The United Nations has some 11,000 peacekeepers in the U.N. Mission in Sierra Leone, known as UNAMSIL.