Libyan authorities shot dead three Sudanese migrants in a western coastal town who tried to escape after they were intercepted by the coast guard in the Mediterranean Sea and returned to shore, the United Nations said Tuesday.

The three were among over 70 Europe-bound migrants, mostly from Sudan, who were returned late Monday to the town of Khoms, said Safa Msehli, a spokesperson for the International Organization for Migration. Khoms is about 120 kilometers (75 miles) east of Tripoli.

The shooting underscores the perils that migrants face in Libya, which has emerged as a major transit point for African and Arab migrants fleeing war and poverty to Europe amid years-long chaos following the 2011 uprising that toppled and killed longtime leader Muammar Gaddafi.

The IOM said local authorities started shooting when the migrants attempted to escape from the disembarkation point.

There was no immediate comment from the U.N.-supported government in the capital, Tripoli. Several calls to a spokesman for the coast guard went unanswered.

Two migrants died at the site of the shooting and a third died of his wounds while being transported to a hospital, according to the U.N. refugee agency, which called for an urgent investigation.

Two other migrants were wounded and were taken to local hospitals while survivors were moved to detention, the IOM said.

“This is not the first time people are subjected to this senseless violence and confirms yet again that no one should be returned to Libya,'' Msehli said.

The director of the International Rescue Committee in Libya, which helped receive the migrants when they arrived on shore, called the shooting “reprehensible.”

“This violence only reinforces the dangers that migrants, refugees and asylum seekers face in Libya. More must urgently be done to ensure their safety and arbitrary detention should end,'' said Tom Garofalo.

IOM Libya Chief of Mission Federico Soda said the shooting came “amid a lack of action to change a system that often fails to provide any degree of protection'' in conflict-sicken Libya.

Last week, an Eritrean asylum-seeker died after arriving at the U.N. refugee center in Tripoli from a trafficking center in Bani Walid in the northwest, UNHCR, the U.N. human rights agency, said.

The young Eritrean arrived at the center with another Eritrean earlier this month. They appeared to be severely malnourished, and one died before it was possible to transport him to a hospital, the agency said.

Since June, more than 100 people have arrived in Tripoli from trafficking centers in Bani Walid. They are often in very poor physical condition and in dire need of assistance, the agency said.

In May, the family of a slain Libyan human trafficker attacked a group of migrants in a smuggling warehouse in the desert town of Mizdah, killing at least 26 Bangladeshi and four African migrants.

Most migrants in Libya attempt to make the perilous journey to European shores in ill-equipped and unsafe rubber boats. The IOM said earlier this year its estimated death toll among migrants who tried to cross the Mediterranean passed the ``grim milestone'' of 20,000 since 2014.

In recent years, the European Union has partnered with the coast guard and other Libyan forces to stop the flow of migrants.

Rights groups say those efforts have left migrants at the mercy of brutal armed groups or confined in squalid and overcrowded detention centers that lack adequate food and water.

The EU agreed earlier this year to end an anti-migrant smuggler operation that involved only surveillance aircraft and instead deploy military ships to concentrate on upholding a widely flouted U.N. arms embargo that's considered key to winding down Libya's relentless war.