Banco Santander SA, the biggest Spanish bank, and National Australia Bank Ltd. are among at least four companies that have expressed interest in buying part of the Royal Bank of Scotland Group PLC's U.K. branch network, said two people with knowledge of the situation.

Banco Bilbao Vizcaya Argentaria SA, Spain's second-largest lender, and Richard Branson's Virgin Money Ltd. are also among the bidders for the 318 branches, said the people who declined to be identified because the talks are private. The deadline for bids was 5 p.m. Tuesday.

Royal Bank of Scotland is selling the outlets to comply with European Union regulations after it received a government bailout in 2008 and 2009.

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