Libya IS convoy comes under attack from 'unidentified aircraft'
The latest report, first conveyed by Reuters, was based on accounts of local residents and could not immediately be verified.
Social media users have since then posted alleged pictures of the strike.
The airforce allied with Libya's western-government confirmed it did not launch the attack.
Sources further added that French military forces were not responsible for the strikes.
The current lack of confirmation raises further questions over the command and control of Libya's airspace.
A number of airstrikes in 2014 and 2015 against a variety of targets were launched from unconfirmed sources.
Most recently, in October 2015, sources of airstrikes against IS group militants, also near Sirte, remained unidentified after US officials denied any involvement.
The unidentified attacks emerge as regional and international powers declare their airstrikes in what is becoming a medley of air fire over Libyan airspace, involving Libyan aircraft and those from the US, France, Egypt and allegedly the UAE.
A series of raids against Islamist militia positions around the city of Tripoli in August 2014 were blamed on the air forces of the UAE and Egypt - but remained unconfirmed.
|Social media users have posted pictures purportedly of the airstrike
Egyptian aircraft launched a series of air raids against the IS group in Libya in February 2015 following the beheading of 21 Coptic Egyptians kidnapped by IS group fighters in Libya.
The US also conducted airstrikes on Libyan targets throughout 2015, targeting both IS group members and figures linked with al-Qaeda.
Earlier in June, news emerged of a confirmed US attack against a leading Tunisian al-Qaeda operative.
Sirte has, for months, been used by the IS group as a base in attempts to expand their presence in Libya.
IS group militants have been trying for several weeks to push east from their coastal stronghold of Sirte.
Officials have warned of crippling consequences if the militants manage to seize control of Libya's oil resources.
Last week IS group launched an offensive against Libya's key oil terminals in Ras Lanouf and nearby al-Sidra, setting ablaze at least four oil storage tanks.
Libya descended into civil war after the October 2011 ousting and killing of Gaddafi, with two governments backed by different militias vying for power and battling over vast energy resources.
The UN Security Council in December approved a resolution supporting a new UN-brokered deal to form a unity government in Libya.