MOSCOW, Jan 13 (Reuters) - Russia’s budget Reserve Fund shrank by $9.4 billion in December, finance ministry data showed on Wednesday, as the government tapped the fund to cover its budget deficit.

The size of the fund was $49.95 billion on Jan. 1, down from $59.35 billion on Dec. 1.

The finance ministry said holdings worth $4.52 billion, 4.14 billion euros and 0.67 billion pounds sterling had been sold in December, equivalent to 710.67 billion roubles.

The Reserve Fund has been shrinking rapidly over recent months, illustrating the strain on government finances caused by low oil prices. On Oct. 1 the fund was worth $70.51 billion. (Reporting by Jason Bush; editing by Jack Stubbs)