NATO planes put on a show of force on Thursday above the Libyan front line, where rebels were following orders to hold back and wait for stepped-up air strikes, against pro-regime forces, to clear their path forward.

The distinct sound of the warplanes, flying too high to be visible, was nearly constant above Ajdabiya, the eastern town that has been a battle-ground over the past week between the rebels and forces loyal to Colonel Moammer Gaddafi. Previously, their presence was only rarely heard.

The intensified air activity on the front line came as foreign ministers in the NATO alliance met in Berlin under pressure, from France and Britain, for increased bombing against Gaddafi's troops.

It also followed an international meeting in Qatar, which reaffirmed the desire by the West and a few Arab nations to see Gaddafi toppled, and a meeting late on Wednesday, between French President Nicolas Sarkozy and British Prime Minister David Cameron, on how to increase military pressure on Tripoli's regime.

Rebels in Ajdabiya told AFP their commanders were ordering them to sit tight in the town because NATO planes were bombing the road leading west, towards the key oil town of Brega, and beyond that Gaddafi's home town of Sirte and, farther, the capital Tripoli.

"We can't go forward. With the planes flying, it's risky. NATO tells us don't go any further," said one insurgent, Alteira Yussef, 30.

A Western official, speaking to AFP on condition of anonymity, said that French, British and Italian military attachés were now in the rebel stronghold of Benghazi and that they were providing indirect information about the situation at the front line to NATO.

"We are doing our best to get situational awareness to NATO, but we don't represent NATO," the official said, adding that no NATO team was in Benghazi.

"We are trying to persuade NATO to come to provide direct communications. That would be very sensible because they would be able to pass information much quicker," he said.

The official said he was unaware of any instructions from NATO to the rebels to wait for a specific deadline before advancing, but he said the rebels were communicating where they were exactly and saying any forces found beyond that were Gaddafi's.

He added that any reliable front line information was valuable because "it's very confusing for NATO because everyone looks the same" -- with Gaddafi's forces using the same sort of civilian pick-up trucks as the rebels instead of military vehicles.

On the front line west of Ajdabiya, on Thursday, a rebel pick-up truck pulled up with six tan-coloured field radios, indicating they were getting equipment from outside to help with their communications.

Rebels in Ajdabiya said they believed Gaddafi's forces were as close as 20 kilometres (12 miles) west of the town because on Wednesday they found the bodies of three rebel fighters there, apparently killed in an ambush.