The men, from Bangladesh, Nepal, India and Sri Lanka, will be flown to Dubai after the Kuwaiti company that hired them failed to secure enough contract work at dining facilities inside a number of US military bases across Iraq. Their passports have also been taken.

"People are getting shot at," said Manoj Kodithuwakku, a 28-year-old from Sri Lanka, speaking to The Times by mobile phone. The crack of bullets could be heard in the background. "It is pandemonium in here," he said.

The men were flown to Baghdad over the past three months to work for Najlaa International Catering Services, which is a subcontractor to Kellogg Brown and Root (KBR), a major service provider to the US Department of Defence.

Each paid up to $3,000 (£2,000) to middlemen on the promise of work as soon as they arrived. The jobs never materialised. Instead the men are kept inside three, large warehouses surrounded by walls in a secured zone around Baghdad airport.

Access to the area, which also houses US military bases and other entities, is limited so The Times was prevented from entering to witness the exchange.

Testimony from the workers, however, painted a scene of chaos and resentment.

Most gave their passports yesterday to officials from the company following assurances that they would be used facilitate the payment of wages to their families rather than to insert exit visas.

By the morning, however, workers said there was no evidence that any money had been dispatched and there was no sign of their passports.

In addition, five buses were parked outside the compound, prompting fears that Najlaa was preparing to send them home.

Marwan Rizk, chief executive officer of Najlaa, confirmed this suspicion. "They are being demobilized to their respective countries," he told The Times. "It is because some contracts have basically vanished or been rescinded."

Mr Rizk, speaking from Kuwait, said that each man would receive a month's salary upon arrival in Dubai, a transit hub for people travelling from Baghdad. Explaining why the workers who have been in Iraq for longer were not receiving more, he said wages should only kick-in once a worker starts his job, which never happened in this case.

It was unclear whether the men would receive tickets for onward flights home.

Inside the warehouses, Sampa Fernando, 31, also from Sri Lanka, was very upset. "Until now I do not have my passport," he said.

Anger at the situation erupted when two men, described as Iraqi immigration officials, visited the compound. As they left one of the migrant workers lobbed a water bottle in their direction, prompting others to start chucking stones.

A Najlaa manager was also beaten in the foray, prompting Iraqi security guards, who secure the warehouses, to open fire, shooting into the air, according to a number of migrant workers.

"I saw them shoot with my own eyes," said Mr Fernando. "As soon as that happened I ran. Nobody was killed and no one was injured in the shooting." He said that a couple of the workers had cuts on their heads after being accidentally caught in the firing line of the stones.

Iraqi police turned up to calm the situation down.

Some 447 men are due to be flown to Dubai tonight, Mr Kodithuwakku, added.

Mr Fernando pleaded for the US military, which has a base close by, to visit the warehouses and speak to the workers. Each man came to Iraq in the belief that they would work in a dining hall facility on a military camp.

"If the US army comes, we can talk to them," Mr Fernando, a father of two, said. "We want to work. We need to work with the US Army.

"We came here to work for KBR, which works for the US army. We would like to talk with them so that they can take action and decide if we are good or not. This is a very bad situation in here. We need help."

A US military spokesman, in response to questions on the case, said: "We take every allegation of human rights violation seriously and are looking into the issue to ascertain the facts. Until that time, we will reserve comment on the issue."