More than 3,000 migrants and refugees were expelled from the North African country in September, HRW said.
Algerian security forces have arrested thousands of migrants and refugees, cramming them onto trucks and buses before expelling them across the border to Niger, Human Rights Watch said.
“Since early September, Algeria has expelled over 3,400 migrants of at least 20 nationalities to Niger, including 430 children and 240 women,” the rights watchdog said on Friday.
“This brings the number of people summarily expelled to Niger this year to over 16,000 – a little over half of them to Niger.”
Landlocked Niger is on a key cross-Saharan route for African migrants trying to reach the Mediterranean and then cross to Europe.
“Algeria is entitled to protect its borders, but not to arbitrarily detain and collectively expel migrants, including children and asylum seekers, without a trace of due process,” said Lauren Seibert, refugee and migrant rights researcher at Human Rights Watch.
“Before moving to deport anyone, authorities should verify their immigration or asylum status individually and ensure individual court reviews.”
Some of the deportees interviewed by the rights watchdog said they had been abandoned at border crossings and told “the way to Niger”. Others said they were stripped of all their belongings before being told to leave.
“I had no shoes, I walked barefoot. It took us five or six hours,” said Tamara from the Ivory Coast.
“They told us, ‘you came to Algeria with nothing, and you will leave with nothing’,” the 28-year-old said.
Algeria has carried out waves of deportations in recent years, including an estimated 25,000 to Niger in 2018, and another 25,000 in 2019, HRW added.
There was no immediate response from the government in Algiers.
Al Jazeera and News agencies