Britain's state-rescued Royal Bank of Scotland on Thursday set aside another £3.1 billion ($3.9 billion, 3.6 billion euros) for US fines over the alleged mis-selling of mortgage securities before the 2008 financial crisis.

The lender, which is 73-percent owned by the British government after a vast bailout, added in a statement that this took the group's total provision to £6.7 billion.