Authorities in Iraq say they have uncovered an al Qaeda cell working to produce poison gas at two locations in Baghdad for future attacks both home and abroad.
Mohamed al Askari, spokesman for Iraq's defence ministry, said five suspects had been detained over the construction of two facilities in the capital to produce sarin and mustard gas, using instructions from another al Qaeda group.
Four hooded suspects - three in bright yellow jumpsuits and one in a brown one - were presented at a news conference on Saturday which included a table display of beakers and jars of chemical compounds.
A pair of soldiers wearing gas masks and gloves brought out containers containing alleged chemical ingredients.
The members of the cell were prepared to launch attacks domestically, and also had a network to smuggle the toxins to neighbouring countries, and also to Europe and North America, said Mr Al Askari.
He said the group had managed to acquire some raw materials and formulas, but they had not produced any active chemical weapons. It was unclear how far along they were in their efforts.
The arrests follow a joint operation between Iraqi and foreign intelligence services.
On Friday, authorities imposed a sweeping ban on temporary license plates for cars across the Iraqi capital in an apparent effort to thwart car bombings.
The temporary black plates are common in post-war Iraq, where for years it was difficult to obtain new ones.
They are typically on older-model vehicles and are more difficult to trace, and authorities say they are frequently used in car bombings.
The heightened security measures come as the Shiite faithful begin making an annual pilgrimage to the shrine of eighth-century Shiite saint Imam Moussa al Kadhim in Baghdad.
While violence has mainly targeted the government and members of the Shiite majority in the past, recent unrest has been more wide-ranging, with attacks on Sunnis as well.
Former Iraqi dictator Saddam Hussein's forces used poison gas to attack the Kurdish town of Halabja in 1988, killing an estimated 5,000 people.
Al Qaeda front group the Islamic State of Iraq is still active in the country, launching regular attacks against both the government and civilians.