Britain's foreign secretary says "our options are open" on stronger measures against Russia over the crisis in Ukraine, despite a leaked document seeming to suggest the U.K. had ruled out economic sanctions.

London is a key hub for Russian investment, which may make officials reluctant to impose sanctions that would halt the flow of money.

A government briefing document photographed as an adviser carried it on Monday said Britain "should not support, for now, trade sanctions ... or close London's financial center to Russians," but would support visa restrictions and travel bans.

Foreign Secretary William Hague told lawmakers on Tuesday that the document "should not be taken as a guide to the views of the foreign secretary" or the decisions of the government. He said: "Our options remain open."