Authorities in the US have rescued a 20-year-old Indian student, who was held captive for months without access to a bathroom, viciously beaten, and forced to work at three homes by his cousin and two other men in an incident described as "absolutely inhumane and unconscionable."

The victim, whose name was not disclosed, spent months trapped in three homes in the US state of Missouri.

On Wednesday, police descended upon a home on a rural highway in St Charles County. They later arrested Venkatesh R Sattaru, Sravan Varma Penumetcha and Nikhil Verma Penmatsa, and on Thursday charged them with offences including human trafficking, kidnapping and assault.

Police were dispatched to investigate the home after a concerned citizen became aware of his situation and called 911.

The victim is safe and being treated at a hospital for multiple bone fractures, as well as lacerations and injuries covering his entire body, said prosecutor Joe McCulloch.

Over seven months, the men locked the student in a basement and forced him to sleep on an unfinished floor without access to a bathroom, charges say.

He scavenged for scraps in nearby restaurant dumpsters and was beaten with electrical wire, PVC pipe, metal rods, wooden boards, sticks and a water supply hose for a washing machine, St Louis Post-Dispatch, a major regional newspaper, reported.

“It's absolutely inhumane and unconscionable that one human being could treat another human being like this,” said McCulloch at a news conference Thursday.

The three defendants are accused of confining and abusing the victim at three different homes owned by Sattaru in Defiance, Dardenne Prairie and O'Fallon, starting in April 2023, according to St Charles County's official website.

Sattaru was identified by investigators as the ringleader and lives in the O'Fallon home with his wife and children.

The main suspect in the case, Sattaru, 35, is additionally charged with human trafficking for the purpose of slavery and contributing to human trafficking through misuse of documentation.

Penumetcha and Penmatsa live in the home where the student was rescued.

Authorities said the student had come to the US from India last year with hopes of studying at Missouri University of Science and Technology in Rolla. Instead, he was taken to Sattaru's homes beginning in April and was forced to begin chores around 4:30 am, work a full day for Sattaru's IT company and then complete a list of evening tasks.

The student told police he regularly got three hours of sleep on a concrete floor in a locked basement where Sattaru monitored him with a surveillance camera, according to court documents.

If the 20-year-old didn't complete the tasks properly, he was severely beaten. Charges say he was forced to strip down naked and was hit all over his body. He was kicked, stomped and lashed, charges say, and his injuries included previous fractures and breaks that did not heal properly.

No one answered the door at Sattaru's home on Thursday afternoon. None of the three men had attorneys listed in court documents.

“They beat him with their fists, they stomped on him, they beat him with electrical wiring, with PVC pipes,” McCulloch said. “They forced him to sleep in an unfinished basement, they starved him, and limited his access to the public and to restrooms.”

McCulloch commended that citizen for making the rescue possible.

“If you see something, say something. We would much rather check it out and find nothing than have an incident like this that's been going on for nearly a year,” McCulloch said.

Because the three suspects are wealthy and have political connections in India, McCulloch said they are being held at the St. Charles County Jail without bond.

Neighbours in O'Fallon were shaken by the arrests on Thursday.

Many said they'd had pleasant interactions with the family, waving as they passed on the street or playing with children in the cul-de-sac.

“It's shocking, for sure,” said Chirag Shah, who lives down the street from Sattaru's home.

And in Defiance, an unincorporated community of less than 100 people known for its wineries, gift shops and position along the Katy Trail, neighbours watched as police flocked to the home beginning Wednesday morning, the paper reported.

Police were told at first by a man in the home that they couldn't come inside, but the 20-year-old eventually came running from the basement. He was trembling uncontrollably, heavily scarred and suffering from bruising and swelling all over his body, charges say.