UNITED NATIONS: The UN Security Council raised new concerns Thursday about arms flowing from Libya into neighboring countries and thousands of detainees held in secret by militias.

A resolution renewing the mandate of the UN mission in Libya highlighted "the illicit proliferation of all arms and related material of all types" since the fall of Libya's longtime dictator Moamer Kadhafi.

The 15-nation body said heavy and small weapons and surface-to-air missiles were involved and stressed the "negative impact on regional and international peace and security."

"There are suggestions that weapons are going out through the southern borders of Libya to countries in the region," Britain's UN ambassador Mark Lyall Grant said.

"We know that in the immediate aftermath of the overthrow of Kadhafi, quite a number of weapons flowed into Mali and Niger," the envoy told reporters, while adding that the council had no firm information on where the arms are ending up now.

Kadhafi was deposed and killed in October, 2011 and many foreign fighters who had been part of his forces fled taking arms with them.

Western intelligence reports have indicated some of the arms are reaching Al-Qaeda linked groups operating in Sahel countries.

The UN envoy to Libya, Tarek Mitri, told the Council that "formidable" security problems remain, mostly because the government is still weak.

"The country remains awash with unsecured weapons and munitions that continue to pose a regional security risk, given Libya's porous borders," Mitri told envoys.

The council eased an arms embargo so that Libya can now buy non-lethal equipment such as armored cars and body armor without UN permission.

But although Prime Minister Ali Zeidan said last month he wanted the UN to lift the weapons embargo imposed in 2011, no official request was made and diplomats said Zeidan had not raised the matter in talks in New York.

Zeidan said his government was speeding up the training of police and judiciary officials and seeking to end the plight of thousands of people, many from other African countries, held secretly by militias since the fall of Kadhafi.

The council resolution expressed "grave concern" over reports of "mistreatment, torture and extrajudicial executions" in detention centers.

It called for the "immediate release of all foreign nationals illegally detained in Libya."

Mitri said his mission "continues to highlight the plight of detainees, particularly those held in secret detention facilities, including farms and private homes" across Libya.

"We are equally concerned by allegations of a number of deaths in custody," he said, while praising Zeidan's efforts "to build a modern, democratic, and accountable state."