SYDNEY (Reuters) - Commonwealth Bank of Australia , Westpac Banking Corp and Australia and New Zealand Banking Group said they had shut their Sydney CBD branches on Monday after a number of hostages were taken in a central city cafe.

"Due to the police operation in Martin Place Sydney, 12 Westpac branches in Sydney CBD will be closed for the rest of today," Westpac said in a tweet. CBA and ANZ posted similar messages.

Dozens of heavily armed police surrounded the cafe in Martin Place, home to the Reserve Bank of Australia, commercial banks and close to the New South Wales state parliament. Television footage showed several people inside the cafe standing with their hands pressed against the windows.