Representatives of Libya's interim government will join US Secretary of State Antony Blinken as well as the foreign ministers of France and Egypt at the UN-sponsored talks.
During its meeting, the Libya Quartet "condemned the continued violations of the UN arms embargo and emphasized that all external military intervention in Libya is unacceptable."
"These girls and boys will be Syria's young adults in five or 10 years and will, in turn, want a future, economic prospects and political freedoms that the system cannot give them if it doesn't reform," he told AFP.
UNSMIL said it "calls on authorities to ensure an independent, impartial and prompt investigation into this heinous attack on civilians and calls for perpetrators to be brought to justice."