Massachusetts health officials said Sunday that three men have died from COVID-19 related illness, bringing the number of deaths from the novel coronavirus in the state to five.

The men, two in their 70s from Hampden and Berkshire counties, and one in his 90s from Suffolk County, had all been hospitalized, according to the Massachusetts Department of Public Health.

Boston Mayor Marty Walsh said on Twitter he was deeply saddened to learn of the city's first resident to die from COVID-19.

"As one community, we stand with his family and friends in their grief," Walsh tweeted. "And as one community, we stand together, determined to do everything it takes to protect each other, protect the most vulnerable, and limit further loss of life."

As one community, we stand with his family and friends in their grief. And as one community, we stand together, determined to do everything it takes to protect each other, protect the most vulnerable, and limit further loss of life. — Mayor Marty Walsh (@marty_walsh) March 22, 2020

The Berkshire County man who died was reported to have an underlying health condition, but officials said all three men were in an age group that is more likely to experience severe disease from COVID-19 regardless of prior health status.

With the 121 new COVID-19 cases announced Sunday, there are now 646 cases statewide.

For most people, health officials say the new coronavirus causes only mild or moderate symptoms, such as fever and cough. For some, however, especially older adults and people with existing health problems, it can cause more severe illness, including pneumonia.

For the first time since officials began releasing the coronavirus numbers daily, the cases were broken down by age group, as well. Sunday's figures show the majority of cases are actually in people ages 40-49, with 134 cases for that demographic. This is followed by 119 cases in people ages 50-59; 112 cases in people ages 30-39; and 93 cases in people ages 20-29. There are 87 cases in people ages 60-69, and there are 83 cases in people over the age of 70. Massachusetts also reports 18 cases in people under the age of 19.

The majority of the confirmed cases in the Bay State continue to be in Middlesex County with 199 people affected, according to the latest numbers by the health department. Suffolk County now has 126 cases while Norfolk County has 75. There are 60 cases in Essex County.

The number of patients hospitalized continues to grow, as well, with health officials saying Sunday that at least 71 people have required hospitalization, 10 more than figures showed Saturday.

Gov. Charlie Baker reiterated Sunday that he expects to see the number of cases go up as testing continues to expand. More than 6,000 Bay State residents had been tested as of 4 p.m. Sunday for the virus by the State Public Health Laboratory and commercial labs, officials said.

Sunday's new figures came hours after Gov. Baker asked Bay State residents with second homes on Nantucket and Martha's Vineyard to stay on the mainland following Nantucket's decision to issue a shelter-in-place order.

"We have talked to people on both Nantucket and Martha's Vineyard who say a lot of people who have second homes there have been going there," Baker told reporters. "We would prefer they not do that and that they stay on the mainland and don't create additional issues for both of those islands at a point in time when they don't have the level of service capacity in place they typically would have in the summer."

Nantucket's order for residents to stay at home will last at least two weeks and was issued after Nantucket Cottage Hospital confirmed the island's first positive case of COVID-19 Sunday morning.

The three deaths announced Sunday followed a weekend during which the commonwealth's first two COVID-19 related deaths were confirmed in a man in his 80s from Suffolk County and a woman in her 50s from Middlesex County. Health officials have said both had pre-existing health conditions, predisposing them to more severe disease.

Health officials say COVID-19 activity is increasing in Massachusetts. At this time, if people are only mildly symptomatic, health officials say they should speak to their healthcare provider about whether they need to be assessed in person. If not, they should stay at home while they are sick.

Asymptomatic family members should practice social distancing and immediately self-isolate if they develop symptoms, according to health officials.

The public continues to be asked to avoid crowds, stay six feet away from others, not shake hands or hug, and call/Facetime or online chat with friends and loved ones rather than meet face to face.

There have been 15 deaths in New England, with five in Massachusetts, eight in Connecticut, and two in Vermont. There are more than 26,700 confirmed cases of the virus in the United States and at least 340 deaths as of Sunday afternoon.