© Eduardo De Francisco/EPA
A Libyan 'rebel' fires a machine gun at Gaddafi forces in an area west of Misrata. Nato, for obvious reasons, denies issuing formal red lines to the rebels.
Rebel leaders in Misrata feel prepared for battle but say they have been told not to cross certain 'red lines'

Tension between Libyan rebels and Nato commanders is growing over the military tactics being used to put pressure on Colonel Gaddafi's forces.

Rebel leaders in Misrata say they are being urged not to launch further pushes against regime troops to the east of the city, and claim they have been told not to cross certain "red lines", even though they feel prepared for battle.

The frustration on the ground has been heightened by their belief that Gaddafi's troops are demoralised and depleted after nearly three months of conflict.

While coalition officials insist they have not issued any direct orders not to attack, they concede they are worried about civilians being caught up in further chaotic fighting, and do not want rebel troops being accidentally hit in bombing raids by Nato warplanes. These continued on Monday and Tuesday, when Tripoli experienced what were perhaps the heaviest daylight bombardments by Nato since the air strikes began in March.

RAF Typhoon and Tornado jets dropped more than two dozen bombs on Monday alone, targeting the headquarters of the secret police in the heart of the city and a major military base on its outskirts. More than 20 air strikes by low-flying jets were reported yesterday. As the strikes continued into the late afternoon, Libyan state television broadcast a defiant audio address from Gaddafi.

"We will not surrender: we only have one choice to the end! Death, victory, it does not matter, we are not surrendering!" he said, describing the rebels as "bastards".

In Misrata, the Guardian spoke to rebel commanders from the Black Brigade and the Swehdi Brigade, who said they felt constrained from launching pre-emptive assaults. Khalid Alogab, a section commander in the Libyan rebel Black Brigade, said the western alliance had given rebel units firm instructions not to cross into certain areas. "The red line, we cannot cross," he said. "If we get the order from Nato we can go. We can capture Tarhuga (a town to the east) in two hours."

Alogab said orders had come from Misrata command that the Black Brigade was to stay put, and that the alliance had designated the eastern front as a red line. Salem Shneshah, a Black Brigade medic, added: "We should move, we want to move. But Nato told us we must stay here."

On the far side of Misrata, members of the Swehdi brigade - named after the city's most famous resistance hero from the last century, Ramadan Swehdi - told a similar story. "Nato say we must be behind the red lines," said Feraz Swehli, one of Ramadan's ancestors.

Rebel army spokesman Commander Ibrahim Betalmal confirmed that Nato orders, rather than tactical considerations, were preventing his army from pushing forward.

"We have been given instructions to stay on the border," he said. He added: "No doubt Nato will help a great deal in clearing the way forward for us."

Nato says it has not issued formal red lines to the rebels, but acknowledges that there is real danger to their forces if they stray into zones that are being targeted by missile and bombing strikes. The coalition needs to know the areas that are safe to bomb and clear of civilians, said a source. "Nobody wants a return to the kind of confusion there was before. Nato has a very clear duty to ensure that civilians are not caught up in the fighting."

While coalition commanders have great respect for the courage of the rebels, they also fear they remain relatively disorganised.

Describing some of the latest attacks by RAF aircraft in Tripoli, Major General Nick Pope said jets had used guided "paveway" bombs to target a police building from which Gaddafi "was engaged in the brutal repression of the civilian population".