Tripoli:
British jets hit a military barracks in the Libyan capital early Sunday, further intensifying NATO pressure on Libyan leader Moammar Gaddhafi nearly four months into an uprising to end his erratic 42-year rule.
The air strikes on the barracks -- repeated targets of NATO strikes -- were a follow-on the Western alliance's first use of attack helicopters on Saturday.
By intensifying attacks from the air and using helicopters to target government forces who melt into the civilian population for cover, NATO is providing a major boost to Libyan rebel forces who have seized much of the country's east and toeholds in the west.
For example, emboldened rebels in recent days have forced government troops from three western towns and broke the siege of a fourth.
A government official, speaking on condition of anonymity because he was not authorized to speak to reporters, said the Sunday strikes caused no casualties because the barracks were abandoned after having come under repeated NATO attack.
A NATO official, however, said Royal Airforce Tornados fired eight missiles into surface-to-air missile depot in Tripoli. The early Sunday attacks also hit military sites in the town of Tajoura, west of Tripoli.
Saturday's strikes by French and British helicopters went after Libyan troops hiding in populated areas, military vehicles and equipment -- targets often unavailable to higher-flying jet fighters.
Lt. Gen. Charles Bouchard, commander of the Libya operation, said the engagement "demonstrates the unique capabilities brought to bear by attack helicopters."
Until Saturday, NATO had relied aircraft that typically fly above 15,000 feet (4,500 meters) -- nearly three miles (five kilometers). The jets primarily strike government targets but there have been cases where they missed and hit opposition forces by mistake.
The helicopters give the alliance a key advantage in close combat, flying at much lower altitudes.
At a regional security conference in Singapore, the Russian deputy foreign minister said NATO was nearing the start of ground operations in Libya.
"Using attack helicopters, in my view, is the last but one step before the land operation," said Sergei Ivanov.
Russia abstained from a United Nations Security Council resolution vote in March to impose a no-fly zone over Libya. Ivanov said there has been disagreement over how to interpret the scope of the resolution.
In the Saturday attacks, British Apaches hit two targets near the eastern oil town of Brega, according British Maj. Gen. Nick Pope, and separate Royal Air Force planes destroyed another military installation near Brega and two ammunition bunkers at the large Waddan depot in central Libya.
French Gazelle and Tiger helicopters struck 15 military vehicles and five military command buildings, said Col. Thierry Burkhard. All the helicopters returned safely, the French and British said.
Brega is of strategic importance to Libya's oil industry and lies on the Mediterranean coastal road to the capital.
In the early days of the uprising against Gaddhafi, Brega shifted between rebel and loyalist hands, but later the front line settled to the east of the town and under government control.
Gaddhafi's regime has been slowly crumbling from within. A significant number of officers and several Cabinet ministers have defected, and most have expressed support for the opposition. But Gaddhafi shows no signs of leaving power.
Gaddhafi has been seen in public rarely and heard even less frequently since a NATO airstrike on his compound killed one of his sons on April 30. That has led to speculation about the physical and mental condition of the 69-year-old dictator, who has ruled Libya since 1969.