Six precision-guided CBU-105 cluster bombs have been dropped on an Iraqi tank column defending Baghdad, the US military has said.
B-52 bombers can drop the new precision-guided cluster bombs
The new type of bombs, known as wind corrected munitions dispensers, are an upgraded version of older cluster bombs which adapt to wind and weather to hit targets more accurately.
The 1,000 lb (454kg) weapons, carried by B-52 bombers and F-16 fighters, each contain 10 armour-destroying bomblets.
The bomblets are released and dispersed by parachute when the bomb's main canister breaks apart after it is dropped.
A range of bomblets can be employed to attack different targets such as armoured vehicles or people, or to start fires.
Traditionally, cluster bombs can cover a large area but do not have precision guidance. Dropped from medium to high altitudes, they can wander off target.
Cluster bomb facts
Tail fins cause weapon to spin as it falls
Canister releases bomblets at pre-set altitudes
Typical coverage of traditional weapons ranges from 650 - 1,300 ft
There is a significant "dud rate" of about 5%. In other words, many do not explode but, rather like landmines, litter the ground with the potential to explode years later.
They are highly controversial weapons, which are strongly opposed by many human rights organisations which say they present an unnecessary risk to civilians.
The upgraded CBU-105s are essentially traditional models fitted with what is called a wind correcting tail kit, which steers them to their targets.
They are referred to as "smart-guided" cluster bombs, and intended to achieve an accuracy of within 30 feet.
Older cluster bombs can be used at altitudes of 200 to 20,000 feet, and at speeds of up to 650 knots.
The new-type CBU-105 weapons can be dropped from double this maximum height - 40,000 feet - and steered to a target about nine miles away.