Grand-Bassam (Ivory Coast) (AFP) - European and African leaders have set themselves a tall order to stamp out horrific abuse of African migrants in Libya, where thousands are suffering in a vast, lawless territory.

On Thursday, a summit of the African Union and European Union (EU) set a goal of immediately repatriating 3,800 migrants languishing in a camp near Tripoli.

Hundreds of thousands more -- "400,000 to 700,000," according to AU Commission head Moussa Faki Mahamat -- remain stranded.

But experts point to a daunting array of hurdles, from extracting migrants in perilous situations to giving them incentives to stay put once back home.

Even so, the summit's commitment, initiated by outrage over a CNN television report on black Africans being sold as slaves in Libya, is being welcomed.

"It is a step in the right direction," International Organization for Migration (IOM) Europe Director Eugenio Ambrosi told AFP by phone from Brussels.

"It is a little bit too much to think it will solve the slavery issue, but it would definitely mitigate (it) to some extent," Ambrosi said.

He said the summit showed there was now "international watchdog pressure" that can be brought to bear on the criminal gangs but it must be "sustained."

The drive was announced at a meeting on the summit sidelines organised by French President Emmanuel Macron.

Macron said the UN-backed Libyan government of Prime Minister Fayez al-Sarraj had identified and granted access to the worst camps to enable the returns of people who want to go home.

The Macron group has decided to work with a task force, involving sharing police and intelligence services to "dismantle the networks and their financing and detain traffickers," he said.

They pledged to freeze the assets of identified traffickers. The AU will set up an investigative panel and the UN could take cases before the International Court of Justice.

- Huge challenge -

Despite those commitments, commentators pointed to big practical problems, which begin with the need for African countries to respond rapidly to the need for travel documents so that evacuees can leave quickly.

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"Something has to be done for people in this situation, obviously, but from an operational and logistical point of view, the evacuations are very complicated," said Matthieu Tardis, a researcher at the French Institute of International Relations in Paris.

African diplomats warned that as long as the key issues of insecurity and poverty on their continent were not resolved the migration problem would remain.

"You can have as many Frontex (EU border and coastguard agency) agents as you want," Algerian Foreign Minister Abdelkader Messahel told a Mediterranean dialogue meeting of African and EU states in Rome.

"If you want no migrants, you have to target development, security" first, Messhel said.

"I think we can do better" than what was being proposed in Abidjan, he said.

Niger counterpart Ibrahim Yacoubou added that "without a durable solution the problem won't be resolved."

Libya's UN-backed Government of National Accord (GNA) is opposed by a rival administration in the east of the country, backed by strongman Khalifa Haftar.

- Long-term help -

Yves Roland Houeto, coordinator of an Ivorian NGO called the Pan-African Association of Children and Young Workers, said he saw no signs West African governments were ready to offer serious economic prospects to keep their young at home.

Governments cannot just offer returning migrants some money and supplies when they land back in their country's airport, he said.

"As soon as their supplies and money run out, they will leave again," Houeto told AFP in Grand Bassam, a coastal city of 80,000 people less than an hour's drive from Abidjan. Every month, around 10 young people leave the area for Europe, he said.

In Nigeria, the National Emergency Management Agency (NEMA) on Friday said 1,295 nationals who were stranded in Libya while trying to get to Europe had returned home voluntarily in November. The figure for October was 826.