The Unite union said drivers working for various operators under the publicly controlled Bee Network have rejected pay offers ranging between 3.5 and 6% after months of negotiations.
Regional officer Colin Hayden said: “The strikes this week, as well as the further action we have called, will cause travel chaos in Greater Manchester.”
Unite has said further strikes involving Stagecoach, First Bus Rochdale and Metroline staff on Manchester’s Bee Network would take place from 30 September to 2 October in addition to this weekend if an agreement is not reached.
Metroline Manchester, Stagecoach Manchester and First Bus Rochdale said they were committed to finding a resolution.
Mr Vaughan said: “Unfortunately for us we can’t step in and intervene directly, so pay is a matter for the bus operators with the union.
“We’ve been encouraging them all through the pay talks process to try to find an arrangement.
“Our primary concern is passengers and it’s really disappointing to see strikes the first time on the Bee Network.”
A full list of affected bus services can be found on the Bee Network website, external.