Fifteen bodies were found on a beach near the Libyan city of Sabratha, some of them burned, the Libyan Red Crescent said.
The group did not identify the dead or say how they had died, but human rights groups said they were likely migrants.
After being notified by authorities, Red Crescent volunteers recovered the bodies and took them to the city morgue, the group said.
Some were found inside a burned-out boat while others were nearby, it said.
Authorities have not commented on the latest grim discovery but Libyan media reported a “dispute between people smugglers” that led to them opening fire on a group of migrants.
One of the groups involved had set fire to the boat on Friday, they added.
Photos apparently showing the boat on fire were widely shared online.
Libya was a key route for clandestine migration towards Europe even before the 2011 uprising that overthrew dictator Moamer Kadhafi.
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The lawlessness that ensued bolstered its position on the world’s deadliest migration route.
People smugglers from the western city of Sabratha — some 300 kilometres (185 miles) from the Italian island of Lampedusa — continue to play a key role.
Migrants often face horrific treatment at the hands of smuggling gangs, and rights groups have repeatedly accused authorities and armed groups operating under state auspices of torture and other abuses.
Since the start of the year, more than 14,000 migrants have been intercepted and returned to Libya, the International Organization for Migration (IOM) said Monday.
