“Long runs started off a bit more competitive but even there we need to fine-tune a few things.
“The one-lap pace is quite far off. Of course it is quite unique conditions and very cold and we need to understand what we are doing wrong at the moment.
“It feels massively tyre-related, the balance is not that wrong, but we have no grip. It is like driving on ice at the moment.”
Hamilton was 0.011 seconds quicker than Norris in the second session, and 0.396secs clear of Russell in the first.
Hamilton, who admitted on Wednesday that he had felt like stopping his season early after a bad race in Brazil last time out, said: “It’s the first time I’ve had a day like that this year. The car was feeling really good in P1. In P2 less so.
“Difficult to know exactly where we are or exactly why we are where we are. But really enjoying driving the track. We’ll see whether the car is still the same tomorrow.
“The race pace is not that great, the work I have to do overnight is to figure out how I can have better race pace without losing pace through the lap. But it was nice to get consecutive sectors and the car not throwing me off.”
Russell said: “Incredible day and I’d love to tell you why and to be honest we are scratching our heads a little bit.
“It was only practice and Lewis did a really great job out there. He has been really on it.
“But the car has just been working. We’re on a street track, its low grip, it’s getting faster and faster every lap. Because we were fast today it doesn’t mean we are going to replicate it tomorrow when the track will be probably three seconds faster.”
Between the sessions, Mercedes team principal Toto Wolff played down the significance of his team setting the pace, saying they were the “low-grip champions”.
“P1 is always good and then when the grip kicks in, performance deteriorates,” Wolff said.
But Russell said he did not see things the same way.
“The perception of us losing performance is not quite fair,” he said. “It’s more the competitors don’t use their high power and might be running a bit more fuel than us on Friday so historically they have been sandbagging a little bit more.
“There is a possibility that might happen tomorrow but the gap we have been showing has been pretty substantial and I hope we can continue that form.”
Russell ended the second session third fastest, ahead of the Ferraris of Carlos Sainz and Charles Leclerc, who had the strongest pace on a race run.