NGO Human Rights Watch accused the EU's border agency Frontex of using a drone to provide information that "facilitates interceptions and returns to Libya ... (despite) overwhelming evidence of torture and exploitation of migrants and refugees".
The migrant-run @RefugeesinLibya Twitter account regularly posts images of refugees allegedly killed by Libyan forces or tortured to extort money from their families.
Refugees in the country are "tortured by European taxpayers' money, dehumanized and deprived in all forms," it said in a recent tweet.
That chimes with a report in October by United Nations experts, who said acts of "murder, enslavement, torture, imprisonment (and) rape" against detained migrants in Libya may amount to crimes against humanity.
None of this has stopped the European Union funding and working closely with the Libyan coast guard to prevent migrants reaching northern Mediterranean shores.
The accusations against Europe are not limited to financial support.
Alarm Phone, a group running a hotline for migrants needing rescue, this month accused Malta of failing to launch operations to rescue migrants in danger, "despite their obligations to do so" under international law.
"Alarm Phone has witnessed this non-assistance policy in action innumerable times," it said, accusing Malta of "abandoning boats at risk of capsizing" within the island's search and rescue zone.
From the start of January until August 20, almost 13,000 migrants have been intercepted and dragged back to detention in Libya while trying to cross the Mediterranean, according to the International Organization for Migration (IOM).
Some have been detained, while others have been sent home or simply allowed to leave the overcrowded detention centers.
A further 918 were either dead or missing.
Libyan authorities deny reports that migrants are abused.
"The arrests are carried out according to the rules in place," a migration official said.
But many argue that the long years of lawlessness since a NATO-backed revolt toppled and killed longtime dictator Moamer Kadhafi in 2011 has left the country prey to armed groups and people traffickers.
"Human rights? There are no human rights in Libya," said Hussein, another migrant stuck in Tripoli.
The 26-year-old from Sudan said he had tried to reach Europe on an overnight boat crossing in 2017.
"The Libyan coast guard caught us and sent us back," he said.
He was detained for a day before managing to escape, he said.
He called on African countries to "look after their people" and discourage them from leaving, "instead of European countries funding Libya to stop migration".