At dozens of events in recent weeks, a New York advocacy group has offered a mini-survival guide for undocumented immigrants under the Trump administration.

First, don't open the door to immigration agents unless you see a warrant signed by a judge. Make a plan for who will take care of your children if you are detained. Know in advance how to get legal help. And alert others in your neighbourhood.

Across the United States, immigrant communities are bracing for an increase in deportations with fear, defiance and preparation.

Story continues below advertisement

In this photo taken Feb. 7, 2017, an arrest is made during a targeted enforcement operation conducted by U.S. Immigration and Customs Enforcement (ICE). Charles Reed/U.S. Immigration and Customs Enforcement via AP

On Tuesday, those fears became more concrete as the U.S. Department of Homeland Security unveiled sweeping changes to the way immigration agents do their jobs with the goal of increasing enforcement throughout the country.

Immigrant communities and advocacy groups are already on high alert. In recent weeks, they say, there have been signs that immigration authorities are intensifying efforts to detain people who are in the country illegally.

That in turn has led to a heightened sense of dread and instability for undocumented immigrants and their families, which often include children born in the United States.

Javier Valdes, executive director of Make the Road New York, an organization focused on immigrant families, said that in recent days his group had received panicked calls from members who saw police officers in the street and mistook them for immigration agents.

"People have just started freaking out – and understandably so," Mr. Valdes said. "There is fear but there is anger as well. None of us are going to take this lying down."

There are an estimated 11 million unauthorized immigrants in the United States, according to the Pew Research Center, down from a peak of 12 million in 2007. About 60 per cent of them live in six states: California, Texas, Florida, New York, New Jersey and Illinois.

Members of the family of Guadalupe Garcia de Rayos, left, stand with supporters at a news conference in front of the U.S. Immigration and Customs Enforcement office in Phoenix. AP Photo/Steve Fluty

Several incidents have deepened the sense that the administration of President Donald Trump intends to make a break with past practice. Earlier this month, Guadalupe Garcia de Rayos, a 35-year-old mother in Phoenix, went for a regular check-in with immigration authorities, a condition of her 2009 conviction for using a false Social Security number. Normally, the visits passed without incident and she returned to her family, but this time they detained her and deported her to Mexico. Her two U.S.-born children remain in Arizona.

Story continues below advertisement

In Seattle, meanwhile, immigration authorities detained Daniel Ramirez Medina, a 23-year-old benefiting from protections put in place by former president Barack Obama. The rules provide temporary work permits to people who entered the United States illegally as children but who have lived their whole lives in the country. The U.S. Immigration and Customs Enforcement (ICE) said Mr. Ramirez admitted to being a gang member, something he denies.

Lawyers are challenging Mr. Ramirez's detention. Some are also vowing to fight the Trump administration's policies announced on Tuesday. Omar Jadwat of the American Civil Liberties Union said in a statement that Mr. Trump intends to pursue a "hyper-aggressive mass deportation policy" but "the courts and the public will not allow this un-American dream to become reality."

Rev. Seth Kaper-Dale of the Reformed Church of Highland Park in New Jersey said that there is "tremendous anxiety" among the members of his congregation, which includes undocumented immigrants from Indonesia who have lived in the United States for more than 15 years.

"What's most troubling now is what this is doing to the mental health of our community," Mr. Kaper-Dale said. Children are frightened about the possibility of their parents being taken away, which is sometimes causing behavioural issues at school, he said.

A refugee claimant from Syria is arrested after crossing the border into Canada from the United States Monday, February 20, 2017 near Hemmingford, Que. THE CANADIAN PRESS/Paul Chiasson

The church is preparing to act as a physical sanctuary, if necessary, for undocumented immigrants at risk of deportation, something it already did once back in 2012. In recent years, his community had a kind of respite from immigration enforcement actions, Mr. Kaper-Dale said, but he believes that time is now at an end.

On Tuesday, for example, members of his church accompanied an undocumented immigrant to a regular check-in at a local ICE office. Their role was to reassure and to watch for anything unexpected, like what occurred earlier this month in Phoenix.

Story continues below advertisement

"We just need this President to know he's being cruel," said Mr. Kaper-Dale, who is running for governor of New Jersey on the Green Party ticket. "He's surely not concerned about security. There's nothing secure about creating a state of fear and chaos."

MORE FROM THE GLOBE AND MAIL:

New Trump order expands number of immigrants in U.S. crosshairs Immigration officers will now be able to swiftly deport any illegal immigrant found anywhere in the United States who cannot prove he or she has been in the country longer than two years

Canada won’t abandon Mexico in NAFTA talks, Freeland says Foreign Affairs Minister says it’s too early to talk about what might be up for renegotiation, but that Canada will not strike a bilateral deal with U.S.