The prisoners at the penal colony in St. Petersburg were expecting a visit by officials, thinking it would be some sort of inspection. Instead, men in uniform arrived and offered them amnesty - if they agreed to fight alongside the Russian army in Ukraine.
Over the following days, about a dozen or so left the prison, according to a woman whose boyfriend is serving a sentence there. Speaking on condition of anonymity because she feared reprisals, she said her boyfriend wasn't among the volunteers, although with years left on his sentence, he "couldn't not think about it."
As Russia continues to suffer losses in its invasion of Ukraine, now nearing its sixth month, the Kremlin has refused to announce a full-blown mobilisation - a move that could be very unpopular for President Vladimir Putin. That has led instead to a covert recruitment effort that includes using prisoners to make up the manpower shortage.
This also is happening amid reports that hundreds of Russian soldiers are refusing to fight and trying to quit the military.
"We're seeing a huge outflow of people who want to leave the war zone - those who have been serving for a long time and those who have signed a contract just recently," said Alexei Tabalov, a lawyer who runs the Conscript's School legal aid group.
The group has seen an influx of requests from men who want to terminate their contracts, "and I personally get the impression that everyone who can is ready to run away," Tabalov said in an interview with The Associated Press. "And the Defense Ministry is digging deep to find those it can persuade to serve."
Although the Defence Ministry denies that any "mobilisation activities" are taking place, authorities seem to be pulling out all the stops to bolster enlistment.
Billboards and public transit ads in various regions proclaim, "This is The Job," urging men to join the professional army.
Authorities have set up mobile recruiting centres in some cities, including one at the site of a half marathon in Siberia in May.
Regional administrations are forming "volunteer battalions" that are promoted on state television.
The business daily Kommersant counted at least 40 such entities in 20 regions, with officials promising volunteers monthly salaries ranging from the equivalent of $2,150 (Sh256,584) to nearly $5,500 (Sh656,378), plus bonuses.
The AP saw thousands of openings on job search websites for various military specialists. The British military said this week that Russia had formed a major new ground force called the 3rd Army Corps from "volunteer battalions," seeking men up to age 50 and requiring only a middle-school education, while offering "lucrative cash bonuses" once they are deployed to Ukraine.
But complaints also are surfacing in the media that some aren't getting their promised payments, although those reports can't be independently verified.
In early August, Tabalov said he began receiving multiple requests for legal help from reservists who have been ordered to take part in a two-month training in areas near the border with Ukraine.
The recruitment of prisoners has been going on in recent weeks in as many as seven regions, said Vladimir Osechkin, founder of the Gulagu.net prisoner rights group, citing inmates and their relatives that his group had contacted.
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It's not the first time that authorities have used such a tactic, with the Soviet Union employing "prisoner battalions" during World War II.
Nor is Russia alone. Early in the war, Ukrainian President Volodymyr Zelenskyy promised amnesty to military veterans behind bars if they volunteered to fight, although it remains unclear if anything came out of it.
In the current circumstances, Osechkin said, it isn't the Defense Ministry that's recruiting prisoners - instead, it was Russia's shadowy private military force, the Wagner Group.
Yevgeny Prigozhin, an entrepreneur known as "Putin's chef" because of his catering contracts with the Kremlin and reportedly Wagner's manager and financier, brushed aside reports that he personally visited prisons to recruit convicts, in a written statement released by his representatives this month.
Prigozhin, in fact, denies he has any ties to Wagner, which reportedly has sent military contractors to places like Syria and sub-Saharan Africa.
According to Osechkin, prisoners with military or law enforcement experience were initially offered to go to Ukraine, but that later was extended to inmates with varying backgrounds. He estimated that as of late July, about 1,500 might have applied, lured by promises of big salaries and eventual pardons.
Now, he added, many of those volunteers - or their families - are contacting him and seeking to get out of their commitments, telling him: "I really don't want to go."