Cluster bombs should be immediately banned because they maim and kill a disproportionate number of civilians, a senior United Nations official said Tuesday.

Jan Egeland, the UN undersecretary general for humanitarian affairs, said in Geneva that world leaders should agree on an immediate moratorium on the use of cluster bombs given that they are often left behind by international conflicts and pose a serious threat to civilians.

No international treaties outlaw the use of cluster bombs, although the Geneva Conventions contain laws to protect civilians during conflict. Human rights groups have long opposed the use of the weapons.

"As long as there is no effective ban, these weapons will continue to disproportionately affect civilians, maiming and killing women, children and other vulnerable groups," Egeland said.

"This freeze is essential until the international community puts in place effective legal instruments to address urgent humanitarian concerns about their use."

Speaking at the Review Conference of the Convention on Certain Conventional Weapons, Egeland echoed a call by the International Red Cross to put a stop to the use of the bombs.

On Monday, the International Red Cross said the bombs are unreliable and inaccurate, causing indiscriminate deaths long after they are dropped because they often fail to detonate.

"For nearly 40 years, cluster munitions have been known to cause high levels of death and injury to civilians during and after armed conflicts. Much of this suffering might have been avoided had other more accurate and reliable weapons been chosen," the committee said in a statement.

"After decades of cluster munition use, both the civilian suffering and the burden of clearing these weapons continues to grow relentlessly."

The committee mentioned that civilians continue to die in Laos and Afghanistan because of cluster bombs dropped on those countries in the 1970s and 1980s.

"In addition to the civilian casualties, the presence of unexploded submunitions has made farming a dangerous activity and hindered development and reconstruction. In both countries, the clearance of these weapons has continued for decades and consumes scarce national and international resources," it said.

Cluster bombs are shells that eject many small submunitions or bomblets. They can be packed into artillery shells or dropped from aircraft. A single shell can scatter between 200 to 600 mini-explosives over a wide area.

Appealing to children

According to UN estimates, up to four million bomblets were dropped by Israeli forces in southern Lebanon and about 40 per cent of them did not explode on impact.

The UN Mine Action Co-ordination Centre in southern Lebanon said the density of cluster bombs in southern Lebanon is higher than it is in Kosovo and Iraq, especially in developed areas, and the bombs pose a threat to hundreds of thousands of people.

If left on the ground, a slight disturbance may cause them to explode. As well, they are often appealing to children because they are sometimes attached to small parachutes or are brightly coloured, prompting children to think they are toys.

UN Secretary General Kofi Annan also urged countries at the conference in Geneva on Tuesday to have a look at the 1980 UN Convention on Conventional Weapons to find ways to "reduce and ultimately eliminate the horrendous humanitarian and development impact" of cluster bombs.

"Recent events show that the atrocious, inhumane effects of these weapons — both at the time of their use and after conflict ends — must be addressed immediately, so that civilian populations can start rebuilding their lives," Annan said in a statement.