A Russian helicopter crashed shortly after takeoff in Siberia on Saturday, killing all 18 people aboard, its airline said.
Preliminary information indicated that the aircraft's blades collided with another helicopter that had taken off beforehand from the same pad in Vankor, above the Arctic Circle about 2 600 kilometers northeast of Moscow, UTair said in a statement.
There were 15 passengers and three crew aboard the Mi-8 helicopter, the airline said. The second helicopter landed safely, it added said.
Russian news reports said all the passengers were believed to have been working for a subsidiary of the state oil company Rosneft.
UTair, one of Russia's largest airlines, operates an extensive fleet of helicopters serving Siberian oil fields as well as fixed-wing flights within Russia and to international destinations, mostly in former Soviet republics.
The helicopter that crashed was manufactured in 2010 and the pilot had nearly 6 000 hours of experience, including 2 300 as a captain, the UTair statement said.
Russian air safety has improved since the 1990s, when poor aircraft maintenance, pilot training and official oversight in the wake of the collapse of the Soviet Union resulted in a high crash incidence.
In February, a Saratov Airlines An-148 regional jet crashed about six minutes after takeoff from Moscow's Domodedovo Airport, killing all 71 people aboard. Investigators said the crew had failed to turn on a heating unit, resulting in flawed airspeed readings. A UTair ATR 72 crashed in Siberia in 2012, killing 33 of the 43 people aboard, after failing to be de-iced before takeoff.