Rights groups accuse security forces of wrongfully killing about 2,500 people since Prime Minister Sheikh Hasina came to power in 2009, many of whom were prominent opposition figures.
Hundreds more have been reported missing, and Swedish news portal Netra News this month reports that some have been secretly held for years in a previously unknown prison near a military base.
“We want the immediate release of the detainees from secret detention cells,” said Sanijda Islam, a member of the local Maayer Daak community group that represents the families of the missing.
“The authorities must stop their denial,” Islam told AFP.
Outgoing UN human rights chief Michelle Bachelet visited Bangladesh this month and urged the government to set up an independent body to investigate claims of enforced disappearances.
But at a rally in the capital Dhaka, hundreds of people with photos of their missing relatives urged the UN to conduct its own investigation.
“We want a strong UN-led commission of inquiry,” said Khondoker Ayesha Khatun, whose son was allegedly abducted by security forces in 2016 and has been unseen since.
There was “overwhelming” evidence that authorities were involved in enforced disappearances and Bangladesh should allow a UN investigation, Human Rights Watch’s Meenakshi Ganguly said Tuesday.
“The government of Bangladesh must stop feigning ignorance and work with the UN to provide urgent responses and effective accountability,” she added.
Last year, the United States imposed sanctions on the elite Rapid Action Battalion police unit, along with seven top security officials, for human rights violations.
The government has denied allegations of disappearances and extrajudicial killings, with a minister saying some of the missing have in fact fled Bangladesh.