At least seven people were killed and four others wounded on Tuesday in an airstrike conducted by an unidentified warplane on Ninah Park in Sokna town, around 600 km southeast of Tripoli.
Sources said local and non-resident families were enjoying sulphurous waters inside the park when the airstrike took place.
Women and children were among the victims, the sources added.
Misrata Airbase denied social media rumours that the warplane had taken off from Misrata.
"There were no air missions in that region today, there were only reconnaissance flights in the coastline," the spokesman for the emergency air operations Mohammed Gango confirmed.
The UN-proposed Presidency Council held an urgent meeting in Tripoli to discuss the incident. It also tasked the defence ministry to set up an immediate investigation into the incident.