Preventing more weapons from being smuggled out of country will be difficult, considering the nature of the vast desert nation's borders, the envoy, Ian Martin, told The Associated Press.
"That has to be a priority now, to secure what still remains in Libya," he said. "Over time, the international community can assist Libya and its neighbours with that, but I am afraid there is not a quick and easy solution to that problem."
During the chaos of Libya's 8-month civil war, human rights groups and reporters came across a number of weapons depots that were left unguarded and were looted after Muammar Gaddafi’s fighters fled.
Martin said the unsecured weapons remain a "very, very serious cause for concern". He said they include shoulder-held missiles, mines and ammunition.
Martin noted progress concerning chemical weapons and nuclear material. Last week, Libyan officials said they discovered two new sites with chemical weapons that had not been declared by the Gaddafi regime when it vowed several years ago to stop pursuing non-conventional weapons. Officials also said they found about 7 000 drums of raw uranium.
"That, too, has been secured," Martin said of the latest discoveries, noting that the main issue is now how to dispose of them.
The Gadhafi regime fell with the capture and killing of the dictator on October 20, followed by a declaration of liberation by Libya's new leadership three days later.
The UN mission headed by Martin is designed to help Libya's interim leaders with the transition to democracy.
By late June, Libyans are scheduled to elect a national assembly that would oversee the drafting of a constitution, followed by parliamentary and presidential elections.
The National Transitional Council last week appointed a new prime minister, who is to form a government by mid-month for the transition period. Some Libyan officials have called for a faster transition, warning of a dangerous power vacuum.
Martin said accelerating the elections timetable "is going to be quite difficult, but depends first and foremost on the speed with which they [Libya's interim leaders] can reach the political decisions, and we can't determine that".
Fundamental decisions, including on the preferred electoral system, have not yet been made, he said.
The NTC has acknowledged that it has not established full control over the country. Suspected Gaddafi loyalists are being held in detention centres controlled by semiautonomous armed militias, instead of the NTC. Human rights groups have reported mistreatment of detainees in such lockups.
Martin said the interim authorities have tried to tackle the problem, "but they need to do more, faster, even before a new government is in place".
Jamal Bennour, a prominent Libyan jurist involved in setting up a new judicial system, said that at the moment, the NTC only controls one prison in Tripoli, and courts and prosecutors are functioning at a minimal level.