BENGHAZI, Libya — British and French attack helicopters struck for the first time inside Libya, giving the NATO campaign more muscle against Moammar Gadhafi’s forces. Hours later, Tripoli was hit by another round of airstrikes and at least eight explosions sounded in the capital.

The use of helicopters significantly ramped up NATO’s operations and was a major boost to Libyan rebels, just a day after the fighters forced government troops from three western towns and broke the siege of a fourth. It was yet another erosion of Gadhafi’s power since the eruption in mid-February of the uprising to end his 42-year rule.

NATO said the helicopters struck troops trying to hide in populated areas, military vehicles and equipment. Lt. Gen. Charles Bouchard, commander of the Libya operation, said the engagement “demonstrates the unique capabilities brought to bear by attack helicopters.”

Until now, NATO has relied on attack jets, generally flying above 15,000 feet – nearly three miles high. The jets primarily strike government targets but there have been cases where they missed and hit rebels instead.