Police have urged Tokyo Electric Power Co., Nippon Steel Corp., NKK Corp. and Toppan Printing Co. to cut off long-standing transactions with firms linked to a major underworld syndicate that officials suspect effectively amounted to payoffs, sources said Tuesday.

The four listed companies admitted they conducted transactions with two firms linked to the Otowa-ikka unit of the large crime syndicate Sumiyoshi-kai, but claimed the business was legitimate.

They claim the money was paid to the two firms for the leasing of plants for offices and purchasing of tea products.