City bus services are still being affected after a water main burst early this morning in Brisbane's CBD.

It happened at about 2:00am (AEST) forcing the closure of bus depots in Roma Street and King George Square.

Roma Street has since reopened, and there will be restricted use of King George Square during this afternoon's peak.

State Transport Minister Scott Emerson says it will take a while for repair work to be completed.

"There has been some damage in terms of tile work, some water damage to the ceiling," he said.

"The important thing is we want to make sure we can get it all back and running.

"That will happen from about 3:30pm, I've been advised."