The U.S. has said it will not drop food parcels and cluster bombs in the same areas

WASHINGTON -- The United States has begun broadcasting warnings to people in Afghanistan informing them how to tell the difference between unexploded cluster bomb units and airdropped food parcels -- both of which are yellow.

The warning, broadcast in the Persian and Pashto languages from a flying radio transmitter, comes amid reports of mounting civilian casualties as a result of the U.S.-led strikes on Afghanistan.

Several aid groups as well as the U.N. have expressed fears that unexploded bombs could be picked up or disturbed by civilians, especially children attracted to them by their bright coloring.

The U.S. transmissions, broadcast from a specially fitted out C-130 'Hercules' aircraft, say that the military is taking care not to drop food aid and cluster bombs in the same area.

"Please, please exercise caution when approaching unidentified yellow objects in areas that have recently been bombed" it goes on to say.

The cluster bombs units used in Afghanistan are metal, shaped like a soft drink can and packed with high explosive.

The food aid packages, known as Humanitarian Daily Rations, are square and covered in yellow plastic.

Cluster bombs contain about 200 small so-called 'bomblets' designed to scatter themselves over a large area, targeting troops concentrations and military vehicles.

Villlage hit

The warning is being broadcast from flying radio transmission stations

The bomblets are meant to explode on contact with the ground, but some weapons experts say that on average one in 10 do not detonate and can lie undetected for years.

Last week the U.N. said it had received information that nine people had been killed in the Afghan village of Shakar Qala, close to the city of Heart, after U.S. aircraft mistakenly dropped a cluster bomb on the area.

According to a U.N. demining team, which visited the area shortly afterwards, eight people were killed instantly and a ninth died after picking up an unexploded bomblet.

Both the U.S. and the UK have rejected calls for them to abandon use of cluster bombs saying they are the only effective way of dealing with particular threats such as those posed by armored vehicles.

Cluster bombs were first used by the United States in the Vietnam War and many unexploded bomblets remain a threat today across the three countries of Indochina.

They were also used widely in the air war over Kosovo in 1999 where mine clearing groups say thousands of live bomblets litter the ground.

Last week the charity set up in the name of the late Diana, Princess of Wales, called for a halt to the use of cluster bombs saying they represented a serious long-term threat to civilians.

In a letter in the Times newspaper in London, the charity's chief executive Andrew Purkis said it appeared the lessons of previous conflicts had not been learned.

"There is evidence from Kosovo and the Gulf War that the components of these weapons are prone to missing their targets and fail in significant numbers to explode," he said.

"They then pose a serious long-term threat to civilians and ground forces alike."