KIEV, March 9 - Ukraine's SBU security service does not have evidence showing that Naftogaz Ukrayiny has legally acquired 6.3 billion cubic meters of natural gas once owned by RosUkrEnergo, a top official at President Viktor Yushchenko's office said.

Viktor Baloha, Yushchenko's chief of staff, said government officials have been refusing to show investigators contracts that had been apparently used during the acquisition.