Rebels said the leaflets, seen by Reuters and plainly meant for forces loyal to Muammar Qaddafi, fell directly on positions the rebels had seized in fighting over the past several days in a painstaking advance toward the town of Zlitan, 160 kilometers east of Tripoli.

Some pulled back, fearing NATO planes flying at 15,000 feet might have mistaken them for the enemy.

The episode was indicative of the problems of coordination that have dogged the almost 3-month-old air war, waged from high altitude in support of a ground force of poorly organized rebels pushing in fits and starts through the olive groves and farmland of the Libyan coastline.

French and British forces began using attack helicopters at the start of June in a bid to hasten Qaddafi’s exit.

The fight is coordinated through NATO advisers on the ground in the rebel stronghold of Benghazi.

The leaflets bore a picture of an attack helicopter and a burning tank. In Arabic, they read: “NATO will use all possible means to destroy all armor used against civilians. Stop fighting. When you see these helicopters, it means it is already too late for you.”

There was clear confusion on Tuesday within rebel ranks at the frontline west of Misrata, a port city taken by rebels in weeks of fierce street fighting with pro-Qaddafi forces.

Some said they had pulled back from positions some 10 km short of Zlitan, the next town in their sights en route to Tripoli.

“I hope there’s some coordination between the fighters and NATO,” said Mohammed Gendi, a 31-year-old rebel commander sitting under an olive tree talking to fellow fighters by radio.

“Qaddafi’s forces are far away,” he said. “Is it logical that NATO has no idea we took those positions?“

A voice from the furthest rebel position crackled over the radio. “They dropped the leaflets right on us,” it said.

A NATO official, who declined to be identified, confirmed NATO had dropped leaflets warning of the possibility of attack by combat helicopters, but said they fell closer to Zlitan than to Misrata.

The official said he did not know whether the area was under the control of pro-Qaddafi forces or the rebels.

At the command post in Dafniya, a rebel named Jakup said: “Do I go back or do I go forward? Is it (the leaflet) for Qaddafi or for us?“

Rebels elsewhere in Libya have complained of poor coordination with NATO.

In the Western Mountains, where rebels hold a string of mountain-top towns stretching more than 200 kilometers from the Tunisian border, commanders complain they have no direct contact with NATO but have to call in coordinates and appeal for air strikes through the rebel leaders in Benghazi.

Communications are patchy at best and cost precious time, rebels say. They often resort to Skype, when the internet is working.