Horrific tales have been revealed of Malian forces and suspected Russian mercenaries executing nearly 300 people, in central Mali.
Residents told Human Rights Watch that the killings occurred during a four-day operation against Islamist militants in late March.
The human rights organization said that the detained men were ordered to walk in groups of up to 10 people, before being executed without warning.
It quoted a man who witnessed some of the executions as saying: "I was living in terror. Every minute I thought it was my turn to take me away and execute me. Even after I was asked to leave, I was afraid that it would be a trap."
He added, "As I slowly walk away, I place my hand on my chest and hold my breath and wait for a bullet to penetrate my body."
On Saturday, the Malian army admitted that it had killed more than 200 militants in a "large-scale" attack on a "terror outpost" in the village of Mora.
The West African country's military junta denies that mercenaries from Russia's Wagner Group are helping it fight the rebels.
On Tuesday, Germany joined the United States, France and the European Union in calling for an independent investigation, involving the United Nations mission in the country, into what happened in the village of Mora in the Mopti region of central Mali.
In its statement, Human Rights Watch said that a "deliberate massacre" of detainees had been committed.
"The Malian government is responsible for these atrocities, the worst in Mali in a decade, whether carried out by Malian forces or foreign soldiers associated with them," she added.
Human Rights Watch described Mora as being under "near-total control" of al-Qaeda in the Islamic Maghreb.
It quoted a local resident as saying that some of the dead "were actually jihadists, but many others were killed simply because they were forced by these jihadists to shorten their pants and grow beards."
Others said the killings were ethnically based, with the targeting of the Fulani, semi-nomadic Muslim pastoralists known in Mali as "Bouleh".
what happened?
Human Rights Watch said it learned from 19 witnesses, from Mora and six other villages, that the soldiers arrived by helicopter near a livestock market on March 27 and exchanged fire for 15 minutes with about 30 Islamist fighters.
The organization stated that "traders in the market and security sources said that several Islamist fighters, a few civilians and two foreign soldiers were killed during this, and during another exchange of fire that occurred on the same day."
Then Malian soldiers and more than 100 members of a foreign force - identified by several sources as Russian - deployed to Mora in a four-day operation.
"After cordoning off the area, soldiers patrolled the town, executed several men as they tried to escape, and arrested hundreds of unarmed men from the market and their homes," Human Rights Watch said.
Mali, a former French colony, maintained strong relations with France after independence in 1960.