WASHINGTON – Libyan military commanders loyal to Moammar Gadhafi are blunting the impact of NATO’s air campaign by hiding tanks and artillery in densely populated areas where the alliance’s fighter planes cannot easily reach them, U.S. and European diplomats said Wednesday.

The shift in tactics has meant fewer targets for NATO warplanes, fueling complaints by rebels who say the quality of air support has plummeted since the U.S. turned over command of Libyan operations to NATO.

Opposition leaders say Gadhafi’s forces are inflicting particularly heavy casualties on civilians in the rebel-held city of Misurata, where dug-in loyalists have been operating with little interference from NATO missiles and bombs.

NATO officials in Brussels acknowledged carrying out fewer strikes around Misurata because of fears of inadvertently killing civilians in areas where the Libyan military was cheek by jowl with civilians.

“We have confirmation that in Misurata tanks are being dispersed, being hidden, humans being used as shields in order to prevent NATO sorties to identify targets,” Brig. Gen. Mark van Uhm, NATO’s chief of allied operations, said at NATO headquarters in the Belgian capital.

In Washington, Secretary of State Hillary Rodham Clinton decried the use of civilians as cover and said the tactical shift had complicated NATO’s task.

“It is difficult when you have a force such as is deployed by Gadhafi, insinuating itself into cities, using snipers on rooftops, engaging in violent, terrible behavior that puts so many lives at risk,” Clinton said at a news conference with Italian Foreign Minister Franco Frattini.

But she added that NATO was “performing admirably” under the circumstances.

The complaints about weakened air power came six days after the official transfer of operational command of the air campaign to NATO.

The Obama administration has pressed Western and Arab allies to assume greater responsibility for the Libyan intervention while continuing to provide reconnaissance and refueling support.

But the U.S. pullback has meant a withdrawal of U.S. planes that are particularly effective in providing close air support, such as the twin-jet A-10 Warthog and the AC-130 Spectre gunship.

Western diplomats say the challenge of recognizing military targets hidden among civilian apartments and schools would be daunting regardless of who was in charge of the mission.

In Benghazi, the mood in the streets turned angry Wednesday as demonstrators blasted NATO for reducing the number of airstrikes in recent days.

At the courthouse, which has become a hub for revolutionary activity, about 300 people waved flags and chanted slogans, many of them demanding airstrikes from NATO and arms for the rebels.