MINGORA, Pakistan (Reuters) - Pakistani helicopter gunships and warplanes hit Taliban positions in the militants’ Swat Valley stronghold Saturday, while a curfew prevented civilians from fleeing the fighting.

The struggle in the northwestern valley 130 km (80 miles) from Islamabad has become a test of Pakistan’s resolve to fight a growing insurgency that has alarmed the West.

The military said up to 55 militants were killed in the day’s clashes in Swat and four soldiers wounded, and that several militants had died in separate clashes close to the Afghan border. The figures could not be independently confirmed.

Pakistan’s army went on a full-scale offensive after the government ordered troops to flush out militants from the Islamist stronghold, once an exotic tourist destination.

Fighting had picked up earlier in the week, triggering a civilian exodus. Fears are growing for those still trapped.

“We are feeling so helpless, we want to go but can’t as there is a curfew,” said Sallahudin Khan by telephone from Mingora, Swat’s main town.

“We tried to leave yesterday after authorities relaxed the curfew for a few hours, but couldn’t as the main road leading out of Mingora was literally jammed with the flood of fleeing people,” he said as gunship fire boomed in the background.

Helicopters and warplanes targeted militant hideouts in Mingora and other areas in Swat, military officials said. Militants fired rockets at an army base in Mingora.

Swat administrator Khushal Khan told Reuters the curfew would remain in force throughout the day.

The U.N. refugee agency has said a “massive displacement” is under way. Citing provincial government estimates, it said on Friday up to 200,000 people had left their homes in recent days with a further 300,000 on the move or about to move.

They join 555,000 people displaced from other areas because of fighting since August, the agency said.

Many stay with relatives or friends or find shelter on their own, but officials fear if the crisis is protracted they will join tens of thousands in camps, further straining resources.

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LOOTING

Pakistan’s private Express TV station reported looting at one camp Saturday, showing scenes of scuffles over supplies, but said the situation had been brought under control.

Prime Minister Yusuf Raza Gilani said the government would seek international help for the displaced and the military would do its best to avoid hurting civilians.

“This is not a normal war. This is a guerrilla war. But it is our resolve, it is the resolve of the army that there should be minimum collateral damage,” he told a news conference.

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The fight against militants based near the border with Afghanistan is seen as vital to defeating the Afghan insurgency.

While Swat is not on the border, analysts say it could also become a base for Afghan insurgents as well as for efforts to destabilize nuclear-armed Pakistan’s government.

Up to 15,000 troops have been pitched against between 4,000-5,000 battle-hardened militants in the valley.

“In my area, there is no government, it’s all Taliban,” said Ibrahim Khan, a farmer in the militant stronghold of Matta town.

“They are in full control.”

In an incident that could hurt government efforts to rally support for the offensive, suspected pilotless U.S. drone aircraft fired missiles Saturday at targets in South Waziristan, an al Qaeda and Taliban sanctuary on the Afghanistan border, intelligence officials said.

One official as well as a Taliban source said the missiles killed five militants. Another intelligence official put the death toll at as high as 20.

Hours later, Pakistani security forces killed 18 militants in the same region, the military said. The shootout erupted after militants attacked a military convoy, killing one soldier and wounding two.

U.S. attacks have been criticized for killing civilians and violating sovereignty, and have caused opposition to Islamabad cooperating with Washington in fighting militants.