NEW YORK — New York’s latest plan to tackle both crime and homelessness in subways was rolling into action Monday after police logged more than a half-dozen attacks in trains and stations over the holiday weekend.

Mayor Eric Adams’ plan, announced Friday, involves sending more police, mental health clinicians and social service outreach workers into the subways. Adams spokesperson Fabien Levy said Monday that a “phased-in” implementation was beginning.

The plan notes that many people who use the subways for shelter need help, not handcuffs, but says police will crack down on sleeping, littering, smoking, doing drugs or hanging out in the system. It calls for clearing all passengers out of trains at the ends of their lines, an approach that has waxed and waned over the years.

The Metropolitan Transportation Authority, which runs the subways, “knows that there are people in the subway system who need help and must and will be helped. But they can’t stay in the subway system,” spokesperson Aaron Donovan said Monday.

Adams, a Democrat and onetime transit police officer who took office last month, said Friday that allowing people to live on subways is “cruel and inhumane” to them and unfair to other riders and transit workers.

“The days of turning a blind eye to this growing problem are over,” said Adams, who campaigned on improving public safety.

But Shelly Nortz, a deputy executive director of the nonprofit Coalition for the Homeless, cautioned against “criminalizing homelessness and mental illness” and suggested the city was falling back on policing strategies that had failed in the past.

In recent years, the city has veered between responding to concerns about crime in the subways and complaints about heavy-handed policing there. The last mayor, Democrat Bill de Blasio, at times deployed more police into the system. So did Adams, just last month.

But in the weeks since, a woman was pushed in front of a train and killed under Times Square, a man was shoved onto the tracks and injured at a major hub in lower Manhattan, and even the mayor said he didn’t feel entirely safe riding the nation’s busiest subway system. It carried more than 5 million riders on an average weekday before the coronavirus pandemic; the weekday average is now about 3 million.

Since Adams and Gov. Kathy Hochul announced the new safety plan Friday, six people were stabbed or slashed in subway stations or trains, according to the New York Police Department. Two female teenagers were arrested in one of those attacks, accused of slashing a 74-year-old man in the face, pushing him to the ground and taking his cell phone on Saturday afternoon after he argued with them while they smoked on a train.

On Monday, the Presidents Day holiday, a 58-year-old man was arrested on charges of going after another man with a hatchet around 12:30 a.m. in a Brooklyn subway stop where police were stationed. The victim, who managed to dodge the swinging hatchet, had asked why the attacker was staring at him, police said.

About two hours later, a man hit a woman in the face with a metal pipe aboard a subway train in the Bronx, police said. The woman, who declined medical care, told officers the man lashed out after asking her to stop talking with a friend of hers. No arrest has been made in that case.

Donovan, the MTA spokesperson, said that although investigations into the weekend attacks are in early stages, they “underscore the urgent need” for the new safety plan.

Levy, however, advised New Yorkers not to conflate “isolated acts of violence on the subways” with “the issues of aiding those experiencing homelessness that the mayor’s plan directly addresses.”