Too many people in Massachusetts have let down their guard when it comes to protecting against the coronavirus that has killed more than 10,000 people here since mid-March, so the state must take steps now to slow the spread of the virus or else hospitals will be overrun with COVID-19 patients by the holidays, Gov. Baker said on Monday.

Starting Friday, he announced, everyone above the age of five in Massachusetts will be required to wear a mask or a facecovering indoors and outdoors in public — regardless of whether social distancing is practiced — and restaurants and entertainment venues will be subject to a 9:30 p.m. curfew. The state’s indoor gathering limit will be lowered to 10 people, down from 25, which will be the number for outdoor events.

“The simple truth is this,” said Baker: “Too many of us have become complacent in our daily lives. I know it’s hard for people to hear me say this time and time again, but it’s true: We’re doing much better than many other states and many other countries, but here, too, we’ve let down our guard and we have work to do.”

The governor said his decision to put more restrictive measures in place was made after consultation with public health experts who, he said, “are increasingly concerned about the virus’s spread and the uptick it creates in hospitalizations.” He added that health care workers are becoming alarmed by the state’s recent resurgence.

Boston Mayor Marty Walsh said on Monday morning that he had spoken with Baker about the new orders and strongly supports them. He spoke before the details of Baker’s new orders were made public.

“On Friday, my chief of health and human services, Marty Martinez, talked about the need, potentially, of rolling back restaurants in the city of Boston, the need for potentially having to roll back gatherings. We don’t want to go there,” Walsh said. He added, “Before we take drastic measures and shut everything down, we have to try and control this virus ... what he’s announcing today I support wholeheartedly.”

Violating the governor’s new orders could lead to a fine and Baker said “local communities can enforce them with whatever means they feel is most appropriate.”

Effective 12:01 a.m. Friday, the Department of Public Health will issue a stay at home advisory that tells people to stay home between 10 p.m. and 5 a.m. except to go to work or for essential purposes; casinos, indoor recreation facilities, theaters and other entertainment venues must close by 9:30 p.m.; restaurants must cease table service by 9:30 p.m.; and all non-medical cannabis and liquor sales must end by 9:30 p.m.

“Since Labor Day, which is 55 days ago, the number of new cases per day has grown by almost 300 percent and over the same period of time the number of people hospitalized on a daily basis is increased by 145 percent,” Baker said. “Those trends are obviously heading in the wrong direction ... and the data points to a clear need to do something about these trends.”

The local arm of the National Federation of Independent Business was critical of Baker’s new orders and said the latest steps threaten to further diminish “an already fragile economy and hinder the state’s recovery.”

“It is unfortunate when businesses that worked hard for months dutifully complying with every state guideline, protocol, regulation, restriction, and mandate must now scale back. Just as the state unemployment rate has started trending in the right direction, a statewide rollback will certainly threaten those job gains,” NFIB State Director Christopher Carlozzi said, adding:

“Instead of penalizing businesses playing by the rules that are already experiencing a drop in customers and sales, the state should attempt to take a more targeted approach to curb the spread of the virus.”

The governor said his intention Monday was to announce measures that stop short of shutting businesses down while reducing “the number of opportunities and activities where people gather in groups and get them home with only members of their household.”

“The goal here is to say all this stuff that’s going on that’s indoors, that’s informal, that’s not masked, that’s close contact where people are sharing food and drink and a sofa is just exactly the wrong thing and it’s a big part of why a huge part of the growth in our trend has been in young people who fall into that category,” Baker said.

He added, “I think what we’re trying to say here is by 10 o’clock people should use their heads and be with the people they live with instead of continuing to perpetuate this constant churning of folks, especially in informal settings in places and spaces where there aren’t any rules and there isn’t any guidance and people aren’t adhering to any of the distance or mask rules that are effective at reducing the spread.”

Bob Luz, president and CEO of the Massachusetts Restaurant Association, said restaurants are likely to see more early sittings, noting it’s “uncomfortable” to seat diners at 8 p.m. and expect them to be done by 9:30.

“Shutting restaurants down early doesn’t stop people from gathering,” Luz told Bloomberg Baystate Business Hour Monday afternoon, predicting people will gather instead in unregulated environments so “it actually in my mind potentially enhances the opportunity for this type of gathering.”

Restaurants stand to lose business in connection with two upcoming New England Patriots night games, Luz said, and the policies will also hamper the holiday dining season. “We’re talking about employees that have been ravaged,” he said. “And this is just, you know, another kick in the gut to them.”

There were 2,431 new COVID-19 cases confirmed in Massachusetts over the weekend, 10,013 people with confirmed or probable cases of the virus have died here since mid-March, and the autumn resurgence of the virus appears to be under way. The state has reported more than 1,000 new cases of COVID-19 each day for more than a week.

On Friday, Rhode Island Gov. Gina Raimondo announced that she was cutting her state’s gathering limit from 15 to 10 people, prohibiting spectators at youth sporting events for the next two weeks, curtailing visits at hospitals and nursing homes, and closing indoor athletic facilities for one week. She said Rhode Island was “on a path” to opening a field hospital in the next few weeks, according to WPRI.

Michael P. Norton contributed to this article.