US central command said the American army was using surface-to-surface missiles, in an apparent reference to multiple launch rocket systems which Britain's armoured brigade near Basra also has in its inventory.

These systems, and the US army's longer-range tactical missile system, fire cluster bombs which are spread over a wide area.

Campaigners say they should be banned because some of the "bomblets" fail to explode and present a big danger to civilians similar to that posed by landmines.

Several reliable analysts shared the view that the bombs were being used by the American army but there was no independent confirmation that they had caused civilian casualties, said Richard Lloyd, director of Landmine Action, the UK arm of the International Campaign to Ban Landmines.

"Unexploded ordnance are a forgotten but lethal legacy of every war," he said.

Iraq's information minister, Mohammed Saeed al-Sahaf, said yesterday that US forces had fired the bombs at Najaf, killing 26 civilians and wounding 60.

General Sir Mike Jackson, head of the army, declined to comment on whether British forces were using them.

The Ministry of Defence has admitted that British forces have depleted uranium weapons but it refused on national security grounds to say whether they are armed with cluster bombs.

Challenger 2 tanks of the 7th armoured brigade around Basra are armed with depleted uranium shells. The defence secretary, Geoff Hoon, has suggested there is no evidence that they are dangerous.

Veterans of the first Gulf war and a body of medical opinion say that radioactive dust from the shells can be deadly.