Children are most likely victims of unexploded munitions
At least six children have been killed and seven wounded after a rocket they were playing with in southern Iraq detonated.
The youngsters were playing with the unexploded artillery in Missan governorate when it went off, the United Nations said.
"This tragedy highlights the terrible danger that unexploded ordnance represents all around Iraq," United Nations spokesman David Wimhurst told a press conference in Basra.
Coalition forces have come under increasing pressure to act quickly to clear live armaments in the country.
Kathryn Irwin, of the UN Children's Fund, said the rocket that killed the children was Iraqi.
"There are thousands of stockpiles of weapons in Iraq," she told French news agency AFP.
The United Nations said nine children had been killed, but the British Ministry of Defence put the figure at six.
An MoD spokesman told BBC News Online: "Six children were killed and 10 were injured playing with discarded Iraqi artillery shells in the north of Basra.
"It seems the children were trying to extract its copper when it exploded."
Human Rights Watch has criticised British and American forces for not doing enough to clear unexploded munitions or secure sites containing weaponry.
Coalition forces urged to do more about unexploded ordnance
A spokeswoman told BBC News Online that the US and UK had publicised details of munitions dropped from the air, but not from the ground - making it difficult to gauge the true extent of the problem.
"There are huge numbers of ordnance on the ground - in civilian areas or close to areas where civilians go, so they are a great danger," she said.
"They are a particular hazard to children because they look like toys. Children pick them up and want to play with them."
The International Committee of the Red Cross (ICRC) has reported at least 30 locations in Basra alone that contain unexploded ordnance.
ICRC spokeswoman Tamar al-Rifai told BBC News Online Iraqi doctors were efficiently treating accidental blast victims and Iraqi hospitals were sufficiently equipped to cope with such casualties.
The British army, which has control of Basra, has identified 350 unexploded ordnance sites in the governorate of Missan and cleared 230, according to Major Cameron Day.
The MoD said 'explosive ordnance teams' were in the area trying to identify the sites.