KIEV, Jan. 28 - Ukraine’s security service SBU on Wednesday warned the government against illegal confiscation of $4.5 billion worth of natural gas owned by gas trader RosUkrEnergo and stored the country’s underground gas tanks.

This is the latest in an escalating dispute over more than 10 billion cubic meters of gas that may jeopardize the recent Russian-Ukrainian gas agreement that had resumed Russian gas supplies to the European Union.