The Pentagon has disputed the allegation.
“All of them were killed by the American army,” Reuters chief David Schlesinger told reporters on the sidelines of a media conference in the southern Portuguese resort of Vilamoura, national news agency Lusa reported.
“There is no understanding on the part of the US military regarding the exercise of journalism,” he was quoted by the agency as saying.
“We can’t run the risk that journalists will become targets (in Iraq). We must learn the lessons from these tragic cases.”
Sixty-two journalists have been killed in Iraq since the start of the US-led invasion of Iraq, according to the Brussels-based International Federation of Journalists.
“How can the Pentagon expect us to work under these conditions,” said Mr Schlesinger.
The most recent death occured on November 1 when an Iraqi cameraman working for Reuters was killed while covering fighting near his house in the western city of Ramadi.
The US military says Dhia Najim, 55, died in a gunbattle between Marines and insurgents.
But the Iraqi man’s colleagues and family have said they believe he was shot by a US sniper after fighting had abated.
Another Reuters’ cameraman, Ukrainian citizen Taras Protsyuk, was killed in April 2003 when a US tank opened fire on Palestine hotel in Baghdad.
A cameraman from Spain’s Telecinco television network, Jose Couso, was also killed in the strike, which injured three other reporters.
In October 2003 a Palestinian cameraman for Reuters, Mazin Dana, was shot dead by US soldiers while filming outside Baghdad’s Abu Ghraib prison.
The US military has denied direct responsibility for those deaths as well.
Pentagon spokesman Bryan Whitman told the media conference via satellite from Washington that those incidents were inevitable in a war.
“Media coverage in places of conflict is always dangerous,” Lusa quoted him as saying.
He put the blame for the two deaths at the Palestine Hotel on Iraqi troops resisting the US invasion, who he accused of using civilian structures for military purposes, leading to confusion about what is a legitimate target.
Journalists at the Palestine Hotel, including many working for US-based organisations, had informed US military authorities that they were using the hotel as a base.