Three homeless men filed official notices on Monday that they were preparing to sue the City of New York for harassment by police who cleared them out of their sleeping spaces and threw away their belongings.

"Homelessness is a tragedy, not a crime," said Donna Lieberman, executive director of the New York Civil Liberties Union, which is representing the men. "No matter how much pressure the city is under to address homelessness, all people deserve to be treated with basic humanity."

New York City Mayor Bill de Blasio has stepped up efforts to reduce homelessness in the largest city in the United States, which has one of the country's biggest homeless populations.

RELATED: “Daily nightmare” for families living in NYC shelters, says Stringer

metro.us/new-york/daily-nightmare-for-families-living-in-nyc-shelters-says-stringer/zsJolu---qufkS1mElFJpc/

About 58,000 homeless people sleep in the city's shelters on any given night. Nearly half of them are children. And according to city data, between 3,000 to 4,000 people live on the streets.

Floyd Parks, 61, Timmy Hall, 58, and Jesus Morales, 42, are seeking damages for mental and emotional distress and their trashed possessions, including a social security card, birth certificate and family photographs.

City Hall said the three men had illegally trespassed on school grounds to sleep and were not targeted as part of the city's encampment initiative or any other homeless outreach program.

“Our number one priority in street homeless outreach is to get individuals the shelter and services they deserve," De Blasio spokeswoman Karen Hinton said in a statement.

Hinton said the city would review its protocols for seizing and disposing of the personal property.

As part a $2.6 billion plan to reduce homelessness, de Blasio last week launched the NYC Homeless Outreach and Mobile Engagement S‎treet Action Team, or HOME-STAT, which involves daily sweeps of homeless gathering spots and a database to track people who are displaced.

RELATED: Will this City Hall shake up help solve New York's homeless problem?

De Blasio said the program would help to provide health care services and permanent housing for the homeless, including those with mental illness and drug addiction.

The New York Civil Liberties Union has said its legal action on Monday is the first step in a larger effort to end the supposed clamp-down on the city's homeless.

On Monday, New York City Comptroller Scott Stringer released an audit that showed the city's Department of Homeless Services routinely placed families with children in moldy, rodent-infested shelters and that it also failed to transition families into homes.