They claimed the Americans had spotted the Reuters crew outside the jail half an hour before Mazen Dana was killed and must have realised he was not a guerrilla carrying a rocket-propelled grenade launcher.

The chief executive of Reuters, Tom Glocer, said: "The latest death is hard to bear. That's why I am calling upon the highest levels of the US government for a full and comprehensive investigation into this terrible tragedy."

Dana, 43, is the second Reuters cameraman to be killed since the US-led force invaded Iraq. His death brought to 17 the number of journalists or their assistants who have died in Iraq since the war began on March 20.

The journalist was killed on Sunday when soldiers in two tanks opened fire while he was filming near Abu Ghurayb prison, which had earlier come under mortar attack.

The US army, which has launched an investigation, claimed its soldiers thought his camera was a weapon.

But colleagues who were with the award-winning cameraman when he was killed told a different story.

Nael al-Shyoukhi, a Reuters soundman, said the soldiers "saw us and they knew about our identities and our mission.

"After we filmed we went into the car and prepared to go when a convoy led by a tank arrived and Mazen stepped out of the car to film.

"I followed him and Mazen walked three to four metres. We were noted and seen clearly.

"A soldier on the tank shot at us. I lay on the ground. I heard Mazen and I saw him scream and touching his chest. I cried at the soldier, telling him 'you killed a journalist'. They shouted at me and asked me to step back and I said 'I will step back but please help, please help'."

He said they tried to help but Dana was bleeding heavily. "Mazen took a last breath and died before my eyes."

Stephan Breitner, of France 2 television, added: "We were all there for at least half an hour. They knew we were journalists. After they shot Mazen, they aimed their guns at us. I don't think it was an accident. They are very tense. They are crazy."

Dana's death has once again turned the spotlight on US soldiers and their shoot first, ask questions later tactics in Iraq.

Numerous civilians have been killed by American troops at roadblocks, often without warning.

The shootings have helped to undermine confidence in the US-led coalition among the Iraqi population.

Film that Dana was shooting as he died showed a tank driving toward him. Six shots were heard. The camera appeared to tilt forward and drop to the ground after the first shot.

The US army spokesman, Colonel Guy Shields, said: "Last night we had a terrible tragedy. I can assure you no one feels worse than the soldier who fired the shots."

The New York-based Committee to Protect Journalists, which honoured Dana with an International Press Freedom Award in November 2001 for his work covering conflict in his hometown of Hebron in the West Bank, yesterday wrote to the US defence secretary, Donald Rumsfeld, asking him to conduct a full inquiry.

Meanwhile US army engineers continued to fight a blaze yesterday on Iraq's main oil export pipeline after two attacks by saboteurs last week set it on fire.

Paul Bremer, the US governor of Iraq, said on Sunday the country was losing $7m (£4.4m) a day because of the sabotage of the export pipeline to Turkey.

The pipeline only reopened last Wednesday but was shut down two days later after saboteurs blew a hole in it.