US finds 'Zarqawi car-bomb factory'

US forces engaged in "mopping up" operations in southern Fallujah have discovered a US-made sports utility vehicle with a Texas registration sticker, which they say was used by followers of Iraq's most wanted man, Abu Musab al-Zarqawi.

A "classroom" equipped with drawings of US warplanes, and letters purportedly written by the Jordanian militant himself were found in surrounding buildings on Thursday, leading military officials to suggest the compound had been a command centre for Zarqawi's notorious Tawhid and Jihad group. Bags of sodium nitrate - which can be used for making explosives - were found next to the vehicle, a Ford Explorer.

Zarqawi's group, which has declared itself the Iraqi branch of al-Qa'ida, is thought to be responsible for the beheadings of several Western hostages, including Kenneth Bigley. While US military sources are convinced the group used Fallujah as a base for its operations, Zarqawi has eluded capture. Some Iraqis say US forces are exaggerating his role to divert attention from the fact that the insurgency is home-grown.

Before last year's US-led invasion Zarqawi was a prominent figure in the al-Qa'ida-linked militant organisation Ansar al-Islam based in a remote village in Iraq's Kurdish northern zone. Kurdish security sources say Zarqawi formed his current organisation after American air strikes dislodged Ansar al-Islam from its mountain stronghold in 2003.

Iraqi authorities have acknowledged that Zarqawi escaped the US assault on Fallujah. And with violence rising in other towns, the worry for US and Iraqi authorities is how many other militants have slipped through the net.