Leonardo Sánchez wailed in pain for hours on the deportation flight from Louisiana to West Africa, he and six other detainees said.

He’d been cuffed around his wrists and ankles. A chain around his waist dug into his grossly protruding abdomen — the result of years-old wounds and surgeries that doctors said left his intestines barely inside his body.

Mr. Sánchez, a 49-year-old Cuban, begged for medical attention from several of the Immigration and Customs Enforcement agents on the aircraft.

“I was in pain, crying like a little kid,” he said. But the agents wouldn’t remove his chains or let him use the toilet, he and other detainees said. He wet himself.

Like many of the more than two dozen deportees on the flight with him, Mr. Sánchez said he did not know where he was being taken. Several panicked when they suspected it was Liberia, after one of them saw it written on a sheet of paper held by an ICE official in Louisiana.

When some protested, they were beaten by agents, five of the deportees said. Some were slammed to the ground or struck with blows, several said. One showed cuts along his wrists and bruises around his neck, which he said he received after resisting getting on the plane. Another said some deportees were left screaming in pain.

The planeload of deportees, which arrived in Liberia this month, carried the first of 1,200 people expected to be sent to the West African country by the United States over the next year. The arrangement is one of the largest in a growing number of deals the Trump administration has made to send deportees — including people with court orders protecting them from being sent back to their home countries — to nations halfway across the world where they have no ties.

In recent weeks, the White House has pushed to expand these so-called third-country deportation efforts and boost the number of people expelled from the United States, according to a U.S. official. In July, ICE arrests jumped to nearly 50,000 people, and the administration has focused on deporting people who have been able to remain in the country for years with court orders protecting them from being sent home, another official added.

The New York Times interviewed 10 of the deportees on the flight to Liberia, all of whom described a harrowing journey that included months in detention in the United States and a panicked 14-hour expulsion to Africa, in which agents wrestled and shackled frightened detainees.

Several spoke on the condition of anonymity for fear of reprisals. All of them said they experienced or witnessed what they described as abusive or violent treatment by ICE officials during the course of their deportation or while in detention in the United States.

“They didn’t treat us like people, like human beings,” said Carlos Téllez-Sanchez, a deportee from Venezuela who was expelled to Liberia. “They can say or do anything to you and there’s nothing you can do.”

The White House, Department of Homeland Security and State Department said in statements that the only deportees being sent to third countries are those who cannot be returned to their home nations or refuse to go back.

“As Secretary Rubio has said, we remain unwavering in our commitment to end illegal and mass immigration,” said Tommy Pigott, a State Department spokesman.

When the flight arrived in Liberia’s capital, Monrovia, Mr. Sánchez, the Cuban national, and three others said they refused to disembark, afraid of being abandoned in an unfamiliar country. They said they were forced onto the tarmac by ICE officers who yanked and twisted their handcuffs, pinned them to the ground and pressed their knees directly onto their necks.

Mr. Sánchez said the federal agents knocked him onto the ground and knelt on his bulging abdomen, leaving him in agony, his pants still damp with urine. Other deportees began shouting, “‘You abuser! If he dies, it’s on you!’” Mr. Sánchez and three other deportees said.

The Department of Homeland Security said that no detainees were refused access to the bathroom, that Mr. Sánchez was reviewed and declared fit to fly by medical staff, that his medical needs were addressed on the flight, and that agents did not kneel or press on his abdomen.

It did not address many of the deportees’ other allegations of abuse.

Mr. Sánchez, crying in pain, said he was carried back onto the flight in Liberia with the others. Then, they were then taken to Equatorial Guinea, one of at least 35 countries with which the United States has struck deportation deals, most of them in Africa.

“Basically, they treated us like we were wild animals,” said Carlos Rodríguez, another Cuban national on the flight. “Like beasts.”

‘The Freezer’

Three of the deportees, including 21-year-old Paola Dos Santos, a Brazilian national who was deported to Liberia, said they suffered “psychological torture” from ICE officials while detained in the United States.

Ms. Dos Santos, who said she was detained for 15 months in two separate U.S. facilities, recounted detainees routinely being denied medical care, including pregnant women. One woman who pleaded for information about her son, who had been separated from her, had her hands and ankles tied together, Ms. Dos Santos said: “They tied her like she was a cattle.”

The Department of Homeland Security said that detainees receive “comprehensive medical care” from the moment they enter ICE custody, including dental, mental health services and prenatal and postnatal care.

“No one is being tortured, denied medical care, or beaten in ICE detention facilities,” the department added after publication of this article. To the contrary, it said, there has been a “more than 1,300 percent increase in assaults against our officers.”

Some of the deportees said they were constantly moved from facility to facility, and sometimes kept in detention centers where up to 50 people shared a single toilet. Many said they were held for days in a painfully cold room without beds that they called “the freezer.”

Late last year, Mr. Téllez-Sanchez, the deportee from Venezuela, said he was working at a car dealership in Dallas and looking forward to the birth of his son. He’d been in the United States for five years after a judge granted him an order protecting him from being sent back to his home country, he and a lawyer working with him said. Then in December, he was arrested on a routine visit to renew his work permit.

When he tried to explain to immigration officials that he had a court order preventing his deportation, he said an ICE agent told him to shut up.

He said he witnessed constant verbal abuse by ICE officials while in detention. While parts of the deportees’ accounts could not be independently verified, The Times was able to confirm certain details with lawyers and government officials.

“The whole time, I cooperated,” Mr. Téllez-Sanchez said. “I got a lawyer, I started a legal case. I didn’t want to risk it, I wanted to do the right thing.”

“They didn’t care,” he added.

In eight months of detention, he was moved more than six times, he said. Alma David, the lawyer working with him, said that constantly moving deportees between states was a common tactic by ICE to prevent detainees from launching legal challenges.

“It’s a kind of psychological warfare,” she said.

Deportees are often confused when they are arrested while trying to renew their work permits or asylum papers, unaware that ICE officials are targeting people who have protection orders like Mr. Téllez-Sanchez, said Ms. David.

The administration’s rapid deportations to third countries are being contested in the courts. In February, a judge declared the policy unlawful, but an appeals court has allowed the government to continue the deportations while it reviews the case.

Now, the Trump administration is boosting deportations by sending people “to countries like Liberia where they have zero ties, don’t speak the language and simply cannot imagine surviving,” said Ms. David.