Gun owners sold unwanted weapons to the city of Boston from 10 a.m. to 4 p.m. Saturday in a regional gun buyback called “Your Piece for Peace’’ announced by Mayor Martin J. Walsh the day after the five-year anniversary of the Newtown shooting that left 20 children dead.

Everyone who turned in a gun at one of the city’s eight locations received a $100 Visa gift card, no questions asked.

By Saturday evening, Boston police did not yet have a count of how many guns had been turned in to the city.

“I’m hoping it’s a successful day getting guns off the street,’’ said Walsh as he hosted a dialogue on race in the city at Northeastern University. “If we buy back one gun, and that gun potentially could have killed someone, it’s been successful.’’

Boston police officers have seized about 700 guns so far this year, he said.

Walsh lamented the number of people killed by guns in the city and the availability of firearms.

“It’s just sad that we have to have a gun buyback program,’’ he said.

The Boston program was one of several set to take place in the region Saturday, from Worcester, to Providence, to Hartford. The city of Boston has held gun buybacks in the past, including a year-long program in 2014, which collected 136 guns in its very first week, and 410 by the end of the year.

Anyone who turned in a gun received amnesty, though police will test guns to see if they were used in crimes. No amnesty will be given for any crimes committed with guns turned in.

The city has collected hundreds of guns through similar buyback programs in recent years. Funding for the gift cards that will be handed out Saturday was raised by local hospitals, including MassGeneral Hospital, Boston Medical Center, and Children’s Hospital.

During the rest of the year, said Boston police spokeswoman Officer Rachel McGuire, residents with unwanted guns can turn them in at police stations. If someone is uncomfortable going to a police station, she said, they can contact a clergy member for help, because police work closely with them.

Evan Allen can be reached at evan.allen@globe.com. Follow her on Twitter @evanmallen.