* Insurgents pushed back to Ajdabiyah
* Cars carrying families stream out towards Benghazi
* Humanitarian concerns mount over Misrata
(Adds more from Bani, other details)
By Alexander Dziadosz
AJDABIYAH, Libya, March 30 Libyan rebels fled in headlong retreat from the superior arms and tactics of Muammar Gaddafi's troops on Wednesday, exposing the insurgents' weakness without Western air strikes to tip the scales in their favour.
It had taken more than five days of allied bombardment to destroy government tanks and artillery in the strategic town of Ajdabiyah before rebels rushed in and chased Gaddafi's troops 300 km (200 miles) west in a two-day dash along the coast.
Two days later the rebels have been pushed back to close to where they started.
The Libyan army first ambushed the chaotic caravan of volunteers, supporters and bystanders outside Gaddafi's hometown of Sirte, then outflanked them through the desert, a manoeuvre requiring the sort of discipline the rag-tag rebels lack.
The towns of Nawfaliyah, Bin Jawad and Ras Lanuf fell in quick succession to the lightning government counter-strike.
Rebel spokesman Colonel Ahmad Bani said fighting was going on at Brega, the next town east along the narrow coastal strip that has been the theatre of most of the fighting. But many rebels had pulled back further to the strategic town of Ajdabiyah and regrouped.
"We thought it better to make a tactical withdrawal until we can think of better tactics and a strategy to face this force," said Bani, adding: "One of the defence points will be Ajdabiyah, not the only one."
He appealed for more allied air strikes and heavier weapons. "We are seeking weapons that will be able to destroy the heavy weapons they are using against us such as tanks and artillery."
Dozens of rebel pick-up trucks mounted with machineguns milled around the western gate of Ajdabiyah. Confusion reigned.
Asked what was happening, one rebel said: "We don't know. They say there may be a group of Gaddafi's men coming from the south." That would suggest another big flanking move through the endless desert which pins the coast road to the sea.
Cars carrying families and their belongings streamed out of Ajdabiyah towards the rebel stronghold of Benghazi.
Libya's state news agency said thousands of Libyans carrying olive branches had joined a peace march towards Benghazi.
In town after town, Gaddafi force's have unleashed a fierce bombardment from tanks, artillery and truck-launched Grad rockets which has usually forced rebels to swiftly flee.
"These are our weapons," said rebel fighter Mohammed, pointing to his assault rifle. "We can't fight Grads with them," he said earlier before joining the rush away from the front.
More on Middle East unrest: [nTOPMEAST] [nLDE71O2CH]
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Interactive graphic link.reuters.com/puk87r
Without Western air strikes, the rebels seem unable to make advances or even hold their positions against Gaddafi's armour. Warplanes flew over the battlefield for a time on Wednesday, but there was no evidence of any bombardment of government forces.
Rebel forces lack training, discipline and leadership. There are many different groups of volunteers and decisions are often made only after heated arguments.
When they advance it is often without proper reconnaissance or protection for their flanks. Their courage and enthusiasm notwithstanding, the insurgents tend to flee in disarray whenever Gaddafi forces start sustained firing.
"Whether we advance 50 km (30 miles), or retreat 50 km ... it's a big country. They will go back the next day," rebel spokesman Mustafa Gheriani told reporters in the opposition stronghold of Benghazi.
"This revolution really is only five weeks old. On the political front it is very organised," he said. "Normally it takes six months to train a soldier ... We are talking about citizens who picked up guns to protect their homes."
A conference of 40 governments and international bodies agreed on Tuesday to press on with a NATO-led aerial bombardment of Libyan forces until Gaddafi complied with a U.N. resolution to end violence against civilians.
The Pentagon said on Tuesday 115 strike sorties had been flown against Gaddafi's forces in the previous 24 hours, and 22 Tomahawk cruise missiles had been fired. Britain said two of its Tornado jets had attacked a government armoured vehicle and two artillery pieces outside the besieged western city of Misrata.
Libya's official Jana news agency said air strikes by forces of "the crusader colonial aggression" hit residential areas in the town of Garyan, about 100 km (60 miles) south of Tripoli, on Tuesday. It said several civilian buildings were destroyed and some people wounded.
U.N. Security Council Resolution 1973 sanctions air power to protect Libyan civilians, not to provide close air support to rebel forces. That would also require troops on the ground to guide in the bombs. Without forward air controllers, intervening from the air in such a fluid battle space is fraught with risks.
Air strikes then may not be enough to stop the Libyan desert civil war turning into a stalemate.
The United States, France and Britain have raised the possibility of arming the rebels, though they all stressed no decision had yet been taken. "I'm not ruling it in, I'm not ruling it out," U.S. President Barack Obama told NBC.
Libya's Foreign Ministry said it would be tantamount to aiding terrorists.
Many of the amateur army of teachers, lawyers, engineers, students and the unemployed appear not to know how to properly use even the weapons they already have.
Obama said he had already agreed to provide communications equipment, medical supplies and potentially transport to the Libyan opposition, but no military hardware.
Russia has already accused the allies of overstepping their U.N. remit by carrying out strikes on Gaddafi's ground forces and on Wednesday warned the West against arming the rebels.
Russian Foreign Minister Sergei Lavrov said it was obvious Libya was "ripe for reforms", but Libyans themselves must decide without influence from outside.
"I find it hard to see how the coalition can agree politically to arming the rebels, but without arms I can't see how the rebels can win," said Daniel Keohane of the Institute for Security Studies.
Aid agencies are increasingly worried about a lack of food and medicines, especially in towns such as Misrata where a siege by Gaddafi's forces deprives them of access.
Government troops killed 18 civilians in Misrata on Tuesday, a rebel spokesman in the city said, and soldiers are still shelling and fighting skirmishes with rebels.
"There are skirmishes today. Tanks bombard the city every now and then," he said. "Snipers are still positioned in Tripoli Street (in the centre of Misrata)."
But a blockade of Misrata's Mediterranean port by pro-Gaddafi forces has now ended, allowing two ships to deliver humanitarian aid and evacuate people wounded in the fighting.
Protection of civilians remains the most urgent goal of the air strikes, and British Prime Minister David Cameron accused Gaddafi's supporters of "murderous attacks" on Misrata.
Oil shipments from Africa's third-largest producer have been blocked for weeks due to heavy fighting and western sanctions. A source at Qatar Petroleum said it was struggling to work out how to market Libyan oil on behalf of the rebels.
Britain expelled five Libyan diplomats, described as strong supporters of Gaddafi, saying they could be a security threat.
Libya expelled Reuters correspondent Michael Georgy on Wednesday, without giving a reason. Georgy had been detained for several hours earlier this month after trying to reach Misrata without being escorted by government "minders". (Additional reporting by Maria Golovnina, Angus MacSwan, Edmund Blair, Ibon Villelabeitia, Lamine Chikhi, Hamid Ould Ahmed, Marie-Louise Gumuchian; Writing by Andrew Roche; Editing by Peter Millership)