Manchester United's Paul Pogba celebrates after scoring against Newcastle United at Old Trafford on Saturday.
CNN  — 

Manchester United midfielder Paul Pogba used a triumphant performance for the English Premier League club to highlight the issue of migrants sold into slavery in Libya, after an exclusive CNN investigation last week.

After scoring the third goal in his side’s 4-1 victory over Newcastle United on Saturday, the 24-year-old celebrated with an unconventional handcuff action.

Pogba explained the celebration on Instagram, writing: “While very happy to be back, my prayers go to those suffering slavery in Libya. May Allah be by your side and may this cruelty come to an end!”

It was the French international’s first appearance for Manchester United since September.

CNN’s Nima Elbagir and her crew went to Libya in October after obtaining footage of an underground migrant auction outside the capital, Tripoli. The team saw the sale of at least a dozen men – some for as little as $400.

CNN was told of auctions at nine locations across Libya. Many more are believed to take place each month.

Libya takes action

On Friday, in response to CNN’s report, Libyan officials announced a formal investigation into slave markets, vowing to find and repatriate people who had been sold into slavery.

The International Organization for Migration welcomed the investigation. But its mission chief in Libya warned “that the smuggling networks are becoming stronger, more organized and better equipped.”

The African Union condemned the “despicable” treatment of migrants in Libya brought to light by the CNN report.

The commission’s chairman, Moussa Faki Mahamat, urged Libyan authorities to “do everything in their power to improve the conditions of African migrants on their territory” and expressed the African Union’s “determination to spare no effort to help bring these acts to an end and ensure the respect of the most basic human rights.”

Mahamat said he intends to dispatch an envoy to Libya to discuss the plight of African migrants with the Libyan government.

Paris protests

A man holds a placard reading "No to slavery in Libya" during Saturday's march.

On Saturday, protesters gathered outside the Libyan Embassy in central Paris to denounce the practice and urge authorities to act quickly.

“We have to mobilize. We can’t let this kind of thing happen,” one protester told France 24 at the rally Saturday. “Did we really need to see such shocking pictures before taking a stand? I don’t think so.”

Thousands fleeing conflict or searching for economic opportunity transit in Libya each year, before attempting the final leg of the journey across the Mediterranean Sea to Europe.

The United Nations estimates there are currently 700,000 migrants in Libya, and for years those who have crossed the Mediterranean have shared stories about beatings, kidnapping and enslavement at the hands of brutal smugglers exploiting the escalating crisis.