Sarin bomb raises fear of chemical attacks in Iraq

• Sarin shell explodes near US military convoy, 2 suffer nerve agent exposure

• US officials fear more civilian casualties from unmarked chemical weapons

• Experts doubt chemical weapon find proves existence of Iraqi stockpiles

Key quote

"There can be debris from the past, and that’s a very different thing from having stocks and supplies. I think we need to know more about it" - Hans Blix, Head of UN Monitoring, Verification and Inspection Commission (Unmovic)

Story in full UNITED States officials last night admitted that they fear other munitions filled with sarin may still exist in Iraq - after a roadside shell containing the deadly nerve agent exploded near a US military convoy in Baghdad.

They are also concerned that the shells may not be well-marked and that a release of sarin in a densely populated area - deliberately or by accident - could kill huge numbers of civilians. It is the first time US forces have found an artillery shell containing sarin in Iraq.

Two soldiers who later transported the 155mm artillery round - found "a couple of days ago" - experienced symptoms consistent with low-level nerve agent exposure, said a US official. It appears that two components in the shell, which are designed to combine and create sarin, did not mix on detonation, he added.

The Ministry of Defence said it would look again at whether British troops should start routinely carrying chemical warfare suits and gas masks following the discovery. A spokesman for British forces in Basra said troops had not been regularly carrying nuclear, chemical and biological (NBC) warfare suits and respirators because the threat of a chemical attack was not thought to be serious enough since the fall of Saddam Hussein’s Baathist regime.

"If it is deemed to be necessary to raise the threat levels, then that is what happens and appropriate measures are taken," the spokesman said. "What equipment [the troops] carry is a matter for the commander in the field."

Meanwhile, it was being reported that up to 3,000 extra British troops are to be sent to Iraq to help improve the security situation. The Times newspaper said ministers would announce the deployment this week.

The sarin find was the first confirmed instance of any of the banned materials on which the US and UK based their case for the Iraq war.

The discovery proved that Saddam Hussein did hide stocks of weapons of mass destruction (WMD), according to the Foreign Office minister, Bill Rammell. He said: "It does appear to be in breach of UN Security Council resolutions and it does significantly appear to back up what we have been saying all along, that Saddam did conceal some of his stock. I think that point needs to be made."

But the US defence secretary, Donald Rumsfeld, said the results were from a field test, which can be imperfect, and more analysis needed to be done. "We have to be careful," he said.

Experts cautioned against treating the find as evidence of widespread WMD in Iraq. It is thought any leftover chemical shells are more likely to have been looted from arsenals.

The former top US weapons inspector in Iraq, David Kay, said it was possible the shell was an relic overlooked when Saddam said he had destroyed such weapons in the mid-1990s. He doubted that the shell or nerve agent came from a hidden stockpile, although he did not rule out the possibility.

The former United Nations weapons inspector, Hans Blix, also said the shell was probably a stray weapon scavenged from a dump, and did not signify that Iraq had large stockpiles of such weapons.

Mr Blix said: "There can be debris from the past, and that’s a very different thing from having stocks and supplies. I think we need to know more about it."

Brigadier-General Mark Kimmitt, who announced the find, said he believed the insurgents who planted the explosive did not know that it contained the nerve agent.

He added: "The round had been rigged as an IED (improvised explosive device) which was discovered by a US force convoy. A detonation occurred before the IED could be rendered inoperable. This produced a very small dispersal of agent."

The Iraq Survey Group was tasked with searching for WMD after the overthrow of Saddam’s regime last year. Saddam claimed to have destroyed his chemical and biological weapons, and UN inspectors had uncovered no major finds.

Iraq began producing sarin in 1984 and admitted possessing 790 tonnes of it in 1995. An estimated 5,000 civilians were killed and 10,000 injured when the Iraqi air force bombarded Halabja with mustard gas and other poison gases, including sarin, in March 1988.