Bitcoin is back below $1,000. Overnight selling has pushed the cryptocurrency down 1.10%, or $11, to $989 a coin, and below the psychologically important level for the first time since February 3 as sellers remain in control following the decision by some of China's largest exchanges to block withdrawals.

Last Thursday, following a meeting with the People's Bank of China, Huobi and OK Coin announced customers would be blocked from withdrawing their bitcoins.

The announcement comes following a wild start to 2017 for bitcoin. It rallied more than 20% in the opening week of the year before crashing 35% on fears China would crack down on trading.

Last week's announcement wasn't the first action China's exchanges have taken this year to curb trading. Earlier, they announced they would begin charging a flat fee of 0.2% per transaction.