Thousands of Iraqis have demanded the release of a local TV reporter who threw his shoes at US President George W Bush at a Baghdad news conference.

Crowds gathered in Baghdad's Sadr City district, calling for "hero" Muntadar al-Zaidi to be freed from custody.

Officials at the Iraqi-owned TV station, al-Baghdadiya, called for the release of their journalist, saying he was exercising freedom of expression.

Iraqi officials have described the incident as shameful.

A statement released by the government said Mr Zaidi's actions, which also included him shouting insults at President Bush, "harmed the reputation of Iraqi journalists and Iraqi journalism in general".

Correspondents say the protesters are supporters of Shia cleric Moqtada Sadr - a leading critic of the US presence in Iraq. Smaller protests were reported in Basra and Najaf.

The Iraqi government has demanded an on-air apology from his employer.

An Iraqi official was quoted by the Associated Press as saying that the journalist was being interrogated to determine whether anybody paid him to throw his shoes at President Bush.

He was also being tested for alcohol and drugs, and his shoes were being held as evidence, said the official, speaking on condition of anonymity.

The Cairo-based al-Baghdadiya TV channel said Mr Zaidi should be freed because he had been exercising freedom of expression - something which the Americans had promised to Iraqis on the ousting of former Iraqi leader Saddam Hussein.

"Any measures against Muntadar will be considered the acts of a dictatorial regime," the firm said in a statement.

The programming director for al-Baghdadiya, Muzhir al-Khafaji, described the journalist as a "proud Arab and an open-minded man".

He said he was afraid for Mr Zaidi's safety, adding that the reporter had been arrested by US officials twice before.

"We fear that our correspondents in Iraq will be arrested. We have 200 correspondents there," he added.