Jan 11 (Reuters) - Russia's finance ministry said on Thursday it would switch to foreign currency sales from purchases in the coming weeks after December oil and gas revenues were lower than expected.

The ministry said its sales of foreign currencies and gold for the period from Jan. 15 to Feb. 6 would amount to the equivalent of 69.1 billion roubles ($778.2 million), or 4.1 billion roubles ($46.2 million) per day.

In the previous period, between Dec. 7 and Jan. 12, the ministry had planned to buy foreign currency worth 244.8 billion roubles. ($1 = 88.7975 roubles) (Reporting by Darya Korsunskaya and Alexander Marrow;)