A major crackdown in western Libya has resulted in the detention of at least 4,000 migrants, including hundreds of women and children, officials said Saturday. The U.N. said at least one young migrant was shot dead and 15 others injured, including two in serious conditions, in the crackdown.

The raids took place Friday in the western town of Gargaresh as part of what authorities described as a security campaign against illegal migration and drug trafficking. The Interior Ministry, which led the crackdown, made no mention of any traffickers or smugglers being arrested.

Officials said Friday that 500 illegal migrants had been detained but on Saturday reported that number had reached 4,000.

Gargaresh, a known hub for migrants and refugees, is about 12 kilometers (7.5 miles) west of Tripoli, the Libyan capital. The town has seen several waves of raids on migrants over the years, but the latest one was described by activists as the fiercest so far.

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Since the 2011 NATO-backed uprising that ousted and killed longtime dictator Moammar Gadhafi, Libya has emerged as the dominant transit point for migrants fleeing war and poverty in Africa and the Middle East, hoping for a better life in Europe. Human traffickers have benefited from the chaos in the oil-rich nation and smuggled migrants through the country’s lengthy border with six nations. They then pack desperate migrants into ill-equipped rubber boats in risky voyages through the perilous Central Mediterranean Sea route.

The detained were gathered in a facility in Tripoli called the Collection and Return Center, said police Col. Nouri al-Grettli, head of the center.

He said the migrants have been distributed to detention centers in Tripoli and surrounding towns. Libya’s detention facilities are miserable, overcrowded places where migrants have suffered from abuses and severe ill-treatment, according to rights activists.

A government official said authorities would “deport as many as possible” of the migrants to their home countries. He said many of the detained had lived illegally in Libya for years. The official spoke on condition of anonymity because he was not authorized to brief the media.

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Tarik Lamloum, a Libyan activist working with the Belaady Organization for Human Rights, said the raids involved human rights violations against the migrants, especially in the way some women and children were detained.

Lamloum said many detained migrants have been registered with the U.N. refugee agency UNHCR, as refugees or asylum-seekers.

Vincent Cochetel, the agency’s special envoy for the Central Mediterranean, told The Associated Press that initial reports were that at least one person was killed and 15 injured in the crackdown. He said in some cases security personnel used excessive force and drove people out of their homes.

“We should not be surprised if people are scared and will try to leave by sea,” he said.

Georgette Gagnon, the U.N.’s humanitarian coordinator for Libya, said unarmed migrants were harassed in their homes, beaten and shot in the crackdown which has also seen a communication blackout in Gargaresh.

Among the injured were five by gunshots with two of them being treated in an intensive care unit, she said in a statement late Saturday.

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The statement didn’t elaborate further details.

The crackdown comes amid a spike in crossings and attempted crossings of the Mediterranean Sea to Europe. Libya’s coast guard has intercepted around 25,300 migrants and returned them to Libya’s shores so far this year. Over 1,100 migrants were reported dead or presumed dead off Libya in the first nine months of 2021, but that number is believed to be higher, according to the U.N. migration agency.

Hundreds of migrants were seen in images posted on social media Friday by the Interior Ministry sitting clustered together in a yard with the banner of the Collection and Return Center in the background.

Other images from Gargaresh purporting to show migrants show them with their hands tied behind their backs. An aerial photo showed men lying face down on the ground at a crossroads, with military trucks and guards around them.