NEAR BREGA (AFP) - Libyan rebels beat a fresh retreat from Brega on Sunday after a new bout of fierce fighting over the key oil town, an AFP correspondent reported. Volunteer fighters, who had entered the frontline town just hours earlier, said they were staging a tactical withdrawal after being ambushed by loyalists of veteran strongman Moamer Gaddafi. The AFP correspondent saw some 300 to 400 of them regrouping on the road back into rebel-held territory some 10 km to the east. Loud explosions could still be heard from the outskirts of the city as the rebels best-trained fighters took on the Gaddafi loyalists.Reinforcements were seen heading to the frontline on a minor road into the town. Most of the rebel volunteers acknowledged that they had neither the military training and discipline, nor the knowledge of the terrain to mount a frontal assault on Brega. They said they were dependent on the rebels few trained fighters, most of them defectors from the regular army. There is no commander. We are all together, said Abdul Wahed Agouri, a 28-year-old volunteer. We are not army. We cant move closer to Brega because we dont know where the enemy is. We dont the area. We have to wait for the army (defectors), he said, adding that that might take a few hours or a whole day. Intermittent explosions rocked the desert landscape as the rebel advance guard exchanged rocket and artillery fire with Gaddafi forces inside the town. The AFP correspondent saw three wounded rebels being transported on the back of trucks to a staging point east of the town where they were transferred to regular ambulances to be taken to hospital in the rebel-held city of Ajdabiya to the east. Earlier on Sunday, the rebels had pushed forward to seize the vast university campus on the outskirts of Brega, an AFP correspondent witnessed before the retreat. The town has been the scene of intense exchanges for several days with both sides advancing only to pull back under fire. On Saturday, the rebels had claimed to have recaptured Brega, 800 km east of the capital Tripoli, but pro- Gaddafi snipers were said to be still active and others were apparently holed up in the university. Meanwhile, veteran Libyan diplomat Ali Treiki has resigned from official duties, Arab League sources in Cairo said on Sunday, the latest in a string of officials to abandon the regime of Gaddafi. Treiki, who represented Libya at the United Nations and a former foreign minister, held talks on Sunday in Cairo with Arab League chief Amr Mussa but refused to make any press statements. He has resigned his official duties but did not pledge allegiance to the rebels fighting to overthrow Gaddafi, a league source said. He is the second high profile official to resign this week, after the defection of foreign minister and Gaddafi regime stalwart Mussa Kussa.