Sydney CBD lanes closed as building floods

A large water pipe has burst at a building in Sydney's CBD, causing flooding in one of the city's busiest thoroughfares.

Four fire crews are at the George Street cinema precinct and an additional truck has been called after they were alerted to the flooding about 7.45am on Tuesday, a NSW Fire & Rescue spokesman told AAP.

The Transport Management Centre says two of three northbound lanes are expected to be closed for some time.

Police are directing traffic around Kent Street between Liverpool and Bathurst Street.