Up to 30,000 Eritreans have been abducted since 2007 and taken to Egypt's Sinai to suffer torture and ransom demands, new research says.
The study, presented to the European parliament, says Eritrean and Sudanese security officers are colluding with the kidnap gangs.
At least $600m (£366m) has been extorted from families in ransom payments, it says.
Victims are kidnapped in Ethiopia, Sudan and Eritrea and taken to Sinai.
Eritrea has denied its officials are involved in the kidnappings.
'Chained together'
Most of those targeted are Eritrean refugees fleeing the country, says the report - The Human Trafficking Cycle: Sinai and Beyond.
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Almost every Eritrean knows somebody who has been held hostage”
Meron Estefanos Rights activist
"Their captors are opportunistic criminals looking to profit from their vulnerability," the report says.
"[The victims] are then taken to the Sinai and sold, sometimes more than once, to Bedouin groups living in the Sinai."
The report was authored by Meron Estefanos, an Eritrean human rights activist in Sweden, and Prof Mirjam van Reisen and Dr Conny Rijken of Tilburg University in the Netherlands.
The report says Eritrea's Border Surveillance Unit (BSU) and Sudanese security officials are among the "actors" colluding with the gangs that hold people hostage in the the largely lawless Sinai.
"[The hostages] are chained together without toilets or washing facilities and dehydrated, starved and deprived of sleep," the report says.
"They are subject to threats of death and organ harvesting... Those who attempt to escape are severely tortured."
Ms Meron told the BBC's Focus on Africa radio programme that one of her cousins was freed after a ransom of $37,000 was paid.
The cousin was abducted in Sudan, before being taken to Sinai where her captors tortured and raped her, Ms Meron said.
"Almost every Eritrean knows somebody who has been held hostage. It's a very common thing," she told the BBC.
http://www.bbc.co.uk/news/world-africa-25222336
