Massachuetts will begin offering walk-in service at six COVID-19 mass vaccination sites on Monday.

The six sites — in Boston's Back Bay and Roxbury neighborhoods, Danvers, Dartmouth, Springfield and Natick — will accept residents without an appointment.

"There's walk-up traffic going on, and a bunch of different locations," Baker said. "In fact, a lot of the pop-ups have been operating with walk-up traffic for a while. And I think what you'll see is just an expansion of the existing walk-up stuff as we go forward."

Baker said residents can go to the state's Vaxfidner websiteto either schedule an appointment or learn about the walk-in opportunities.

"Vaxinder will be listing for each of those locations, what the hours are, and other details associated with pursuing walk up appointments," Baker said.

Baker made the announcement from the Encore Boston Harbor casino in Everett, where Cambridge Health Alliance currently operates a vaccination clinic.

"This could be a great new chapter to the program overall," the governor said. "And paired with the targeted, community-based effort that we're pursuing like this one here at Encore, we should be able to reach many more of our residents and build on the national-leading success we've had in distributing vaccines so far."