Dozens of migrants are suffering from malnutrition in a detention center in Libya's capital, an international charity said Thursday.

Doctors Without Borders said its survey showed that over 300 people, including more than 100 children, are being held in the Sabaa detention center in Tripoli. Around 75 detainees are malnourished or underweight, with children significantly more likely to suffer moderate or severe malnutrition, it said. Several people reported receiving only one meal every two to three days, with new arrivals waiting four days before receiving food.

"What we see today in this single detention center is symptomatic of an uncontrolled, unjustified, and reckless system that puts the lives of refugees and migrants at risk," said Karline Kleijer, Doctors Without Borders' head of emergencies.

She urged Libyan authorities to release those held in Sabaa, almost half of whom have been detained for six months or more.

Libya was plunged into chaos after the 2011 uprising that toppled and later killed longtime ruler Moammar Gadhafi, and has since emerged as a major transit point for migrants fleeing war and poverty in Africa and the Middle East and seeking a better life in Europe.

Rights groups say migrants face exploitation and abuse in Libya at the hands of smugglers and local militias.

In recent years, European countries have provided training and funds to Libyan authorities to reduce hazardous sea crossings, which have claimed thousands of lives. But critics say those efforts leave the migrants trapped in Libya.

Sam Turner, head of the Doctors Without Borders mission in Tunisia, said the EU policies to address migration "are directly resulting in people being held in these conditions in Libya."

"It is an extremely cynical approach ... and the cost is human lives," he said.

Last month, Libyan police moved in to end a protest by migrants held at the Trig al-Sikka detention center in Tripoli, setting off clashes in which around 50 people were wounded, according to the U.N.'s migration agency.

Doctors Without Borders says an estimated 670,000 migrants are in Libya, including 5,700 held in detention centers, where they are regularly exposed to human rights abuses including extortion, torture, sexual violence and forced labor.