Russian harbour Murmansk to be extended and improved according to the Weekly Intelligence Summary No. 3 dated 22 January 1921

An item referred to a statement of the Soviet government at Moscow, Russia reporting that the extending and improving of the harbour of Murmansk would be speeded up. There was a proposal to establish a submarine base there suitable for stationing 6-8 submarines.  

Source

The National Archives, Kew Gardens, England CAB-24-118-88