FREETOWN, June 29: A UN helicopter on a routine flight in eastern Sierra Leone crashed into a hillside on Tuesday, killing all 24 people on board, a UN spokeswoman said.

Sheila Dallas said the helicopter, an Mi8-MTV belonging to the Siberian-based UT Air charter company, was on a routine morning flight to the town of Yengema when it was blinded by jungle thicket and crashed into a hill.

"We flew in another helicopter near there, because you can't get any vehicles in there and our soldiers went in on foot," Dallas said by telephone from Freetown. "We can confirm that there were no survivors. All 24 people on board are dead."

Aside from the three-member Russian crew, little is known about the passengers on board. Dallas said the manifest would be released later on Tuesday. The office of UN Secretary General Kofi Annan said from New York that an immediate investigation had been launched.

No details were immediately forthcoming. A spokesman for the charter company that was servicing United Nations troops in the region, Igor Blinov, told Russia's NTV television that the chopper fell on its side, causing a fire in a wooded area of the war-torn country, host to an 11,000-strong UN peacekeeping mission helping to rebuild after a decade of brutal rebel conflict. -AFP