The flight began soon after the rebels were hit by an air strike near the key oil town of Brega which they say was carried out by Nato forces. Two fighters and a paramedic were killed in the strike and 10 more fighters were wounded.
In Brussels, Nato says it is trying to confirm the reports.
The rebels seized Ajdabiya on 26 March, a week afer coalition forces beat back Kadhafi loyalists from the gates of Benghazi. After coming within 60 kilometres of the Libyan leaders's hometown of Sirte on 28 March, the rebels have been steadily pushed back almost 400 kilometres by Kadhafi's forces.
Despite Kadhafi's advances, French Foreign minister Alain Juppé, said on Thursday that is now only a question of how his regime meets its downfall rather than whether the veteran ruler can survive in power.
Meanwhile, the US has rebuffed a letter from Kadhafi to President Barack Obama asking for an end to air strikes on his country. Instead the US reiterated calls for Kadhafi to stand down.