The statement came following reports on the use of banned weaponry in Northern Libya's cities of Bin Jawad and Sirte earlier this year.
"Libyan authorities should investigate these incidents and make sure its forces don't use cluster munitions," the watchdog's Arms Division chief Stephen Goose said as quoted in the statement.
Evidence of the use of banned #cluster bombs in at least 2 locations in #Libya since Dec 2014. http://t.co/uAWFTdjOkV pic.twitter.com/SQUTw8P14u
— Wenzel Michalski (@WenzelMichalski) 15 Март 2015
HRW identified that in both cases remnants of RBK-250 PTAB 2.5M cluster bombs were found and noted that both locations were recently bombed by the Libyan Air Force.
However the watchdog stressed that it was impossible to "determine responsibility on the basis of available evidence."
Cluster munition is a type of explosive weapon that contains and releases large numbers of smaller submunitions over a wide area, making it highly imprecise and endangering anyone in the vicinity including civilians.
Libya is currently facing its worst wave of violence since the beginning of the civil war prompted by the 2011 overthrow of long-standing leader Muammar Gaddafi.
There are now two rival governments in the country, with the self-proclaimed authorities controlling the Libyan capital of Tripoli and adjacent western areas. The internationally recognized government is fighting numerous militias, including offshoots of the Syria and Iraq-based Islamic State.