British Apache helicopters destroyed a radar station and a military checkpoint held by Muammar Gaddafi's forces near Brega in their first sorties over Libya, the defence ministry said on Saturday.
The operation on late Friday by Apaches flying from the helicopter carrier HMS Ocean off the north African coast took place alongside an operation by French helicopters from the assault ship Tonnerre, it said.
"Apache attack helicopters, flying from HMS Ocean, conducted their first operational sorties over Libya last night," Major General Nick Pope, spokesman for the Chief of the Defence Staff, said in a statement.
"The Apaches were tasked with precision strikes against a regime radar installation and a military checkpoint, both located around Brega," he said.
"Hellfire missiles and 30mm cannon were used to destroy the targets; the helicopters then returned safely to HMS Ocean."
The eastern oil town of Brega is roughly where Libyan government and rebel forces have reached a stalemate in recent weeks.
Pope said that the attack was coordinated with other coalition air missions by Nato's air operations centre at Poggio, Italy, "and in particular was planned alongside an operation by French helicopters from the assault ship Tonnerre."
France has said that it deployed Gazelle and Tigre helicopters.
Britain announced just over one week ago that it would deploy four Apaches to join the Nato mission against Gaddafi's forces. It did not say how many of them were involved in the mission overnight.
British defence secretary Liam Fox hailed the mission, which comes less than a year after the coalition government axed Britain's only jet-capable aircraft carrier as part of sweeping cuts.
"This was the first operational mission flown by British Army Apaches at sea," he said.
"Their deployment from HMS Ocean demonstrates the flexibility of not just the aircraft, but also the Royal Navy's Responsive Force Task Group, held at very high readiness for contingency operations around the world."