(CNN) -- Human rights groups in Bangladesh and abroad are calling for an investigation after 16 borders guards accused of participating in a bloody revolt in February died in custody in recent days.
A Bangladesh Rifles soldier is shown wearing a white cloth signifying surrender in late February.
The Bangladesh military acknowledged the deaths of the Bangladesh Rifles paramilitary troops, or jawans -- but insisted they were the result of illness and suicide.
"Given the history of abuses by security forces in Bangladesh, there is no reason to take at face value the claim that these detainees have committed suicide," said Brad Adams, Asia director or the New York-based Human Rights Watch, in a statement.
The 16 were among 1,100 jawans rounded up after a 35-hour mutiny that began on February 25 in the Rifles headquarters in the capital city, Dhaka. The jawans rebelled against their commanding officers, taking dozens of them hostage. When the standoff ended, more than 70 people were found dead -- the majority of them army officers.
Initially, Bangladeshi Prime Minister Sheikh Hasina promised the jawans amnesty if they laid down their arms. But once the scope of the massacre came to light, Hasina withdrew her offer -- saying the government will not show mercy to those who killed, looted or committed arson.
The jawans were issued an ultimatum to turn themselves in, while the government created a committee to probe into the mutiny.
The result of the government inquiry is yet to be made public, after several delays.
On Thursday, the Rifles leadership issued a statement that said 16 detainees have died in custody since March 9: four from suicide, six from heart attacks and six from other diseases.
"We believe that perhaps they have failed to cope with the mental pressure associated with the guilt of committing the brutal attacks,"the statement said.
It then added: "Suicide is seen as a sin in religious terms and is also socially undesirable."
In response, the legal aid group, Ain o Salish Kendro (Law and Adjudication Center), and the Bangladesh National Women Lawyers' Association were among several organizations calling for an investigation.
During a hearing Wednesday, one of the suspects told a Dhaka court he had been administered electric shocks during a seven-day detention.
Family members of other detainees have made similar allegations.
Some of the suspects who died in custody had wounds on their bodies consisted with torture, Human Rights Watch said.
Bangladeshi authorities have said the wounds may have been inflicted when the suspects tried to escape from the Rifles headquarters after the rebellion.
"The explanations given by representatives of the security forces are simply not credible," Adams said. "Torture is a regular 'investigative technique' in Bangladesh and killing of detains in government custody is an endemic problem."
The country's elite anti-crime unit, Rapid Action Battalion (RAB), have often been accused of 'extra-judicial' killings. The battalion is involved in the interrogation of many of the Rifles suspects.
Since its inception in 2004, more than 550 alleged criminals died soon after they were captured by RAB forces. In each case, the battalion claimed the arrested men died from stray bullets as their units were engaged in gun battles with the suspects' comrades.
The 65,000-strong Bangladesh Rifles is responsible primarily for guarding the country's borders, but it also takes part in operations such as monitoring polls.
It is distinct from the army, but their commanders are career army officers.
The troops staged their rebellion on the second day of BDR Week, when officers and troops from various BDR outposts along the border were in the capital for celebrations.
Discontent had been bubbling for years in the ranks of the BDR, who complained their army superiors dismissed their appeals for more pay, subsidized food and their requests to participate in United Nations peacekeeping operations -- which pay far more than what they make at home.
Bangladesh and its South Asian neighbors are the largest troop contributors to U.N. peacekeeping operations.
During the stand-off, dozens of officers were killed. Some bodies were dumped in mass graves. Others were tossed in sewers that emptied into a river, where they floated for miles before being retrieved.