The major earthquake was 866km (538 miles) northeast of Yakutsk, capital of the Sakha Republic - also known as Yakutia.
Flights from east of Russian resumed for the first time since last year's earthquake and tsunami which led to the Fukushima Daiichi nuclear disaster.
The helicopter carrying 17 people lurched on its side on takeoff, with 5 described as being in a 'grave' condition.
Mystery over circumstances of crash when chopper was on 'unsactioned' flight.
A helicopter carrying ammonite - used to break ice - crashed in Irkutsk region after 'exploding in mid air'.
Many residents have refused to leave their homes because of the worst flooding since records began.
Pet Druzhok was evacuated but swam back to stand on the doorstep of his waterlogged house, holding back the tide.
The Usolyekhimprom facility, disused due to bankruptcy in 2017, is a ‘toxic catastrophe waiting to happen’.