As one of the pilots 'lazed' the other week I'm reasonably well qualified to comment.
Green laser - seen from about 4 miles initially - very definitely directed at the aircraft.
In my case the light caused mild 'brown-out' as you can get after NVG use.
No idea of laser power but if you look here -
www.gyroscope.com - you will see you can buy anything up to 100 MW without too much difficulty.
Police are actively following up as they are concerned in case it's pre-targeting. If you do experience this please ensure you report it to ATC who will then info the police.