Seibu Railway Co. provided 400 million yen to a former high-ranking member of an ultranationalist group in the six years to 2003 via a string of transactions involving land in Kanagawa Prefecture, sources said Saturday.

The Tokyo Regional Taxation Bureau, which probed the deals, concluded that the money was essentially a taxable "social expense" designed to curry favor with the 73-year-old ultranationalist, the sources said.

Based on the conclusion, the tax bureau, an arm of the National Tax Agency, has ordered the railway operator to pay more than 100 million yen in back taxes, they said.