The family of American journalist Marie Colvin, who died in the Syrian city of Homs in February 2012, has filed a wrongful death lawsuit in a US court accusing the Syrian government of deliberately killing her.

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The suit alleges that the attack on the apartment where the Sunday Times reporter was staying was part of a plan orchestrated at the highest levels of Bashar al-Assad's regime to silence local and international media

The Syrian military intercepted Colvin's communications and unleashed a barrage of rocket fire on her position in the besieged city of Homs, according to documents filed in US district court in Washington on Saturday.

Colvin, then reporting for the London Sunday Times along with French photographer Remi Ochlik, died when 11 rockets hit a building where they were staying.

British photographer Paul Conroy, French reporter Edith Bouvier, and Syrian media defender Wael al-Omar were injured in the same attack.

The suit alleged that acting "with premeditation, Syrian officials deliberately killed Marie Colvin by launching a targeted rocket attack" against the makeshift broadcast studio in Homs where Colvin and other reporters were based.

The lawsuit is based on information from captured government documents and defectors. It names several Syrian officials, including Mr Assad's brother Maher.

After an informant confirmed Colvin's presence at the site, Syrian artillery units "deliberately launched salvos of rockets and mortars directly at the Media Centre".

"Using a targeting method called 'bracketing', multiple rockets were launched to either side of the Media Centre, drawing closer with each round," the suit stated.

The rocket attack "was the object of a conspiracy" by senior Assad regime officials "to surveil, target, and ultimately kill civilian journalists in order to silence local and international media as part of its effort to crush political opposition," the document reads.

The suit was filed on behalf of Colvin's sister Cathleen Colvin and other surviving family members by the non-profit Centre for Justice and Accountability.

Sorry, this video has expired Family of war correspondent Marie Colvin sues Assad regime

'The plan was to kill journalists and silence them'

Mark Lanpher is a partner with Shearman and Sterling, the firm that filed the lawsuit.

He said there was substantial evidence to back up their claims of regime complicity.

"Her (Colvin's) death was not part of an accident and was not incidental but rather was part of a deliberate plan and conspiracy to kill journalists and silence them," he said.

"Obviously, one doesn't make these kinds of allegations lightly. We as lawyers have obligations to gain evidence so we can back up whatever we are alleging in court.

The lead attorney on the case, Scott Gilmore, said the evidence of former defectors and government sources would form part of the case.

"This case was based upon four years of relentless investigation, until eventually we got government sources and we got to former defectors who had left the country and we able to come forward with their stories and essentially serve as whistleblowers," he said.

"We have documents from the Syrian government showing that as early as August 2011 there was a policy specifically identifying as a threat to the state individuals who are tarnishing the image of Syria in the foreign media.

"That could mean someone simply taking a photo on their cell phone and uploading it to Facebook. Or in the case of Marie Colvin, it could be one of the world's most prominent war correspondent exposing the siege of Homs from the inside on global network news."

Mr Gilmore said after the Syrian government was given confirmation Colvin had been killed "rewards were given to those responsible for providing the key information" that lead to her death.

Just hours before she died Colvin gave an interview with CNN describing the shelling and "complete merciless nature of the bombing".

Colvin, who was 56, covered many of the bloodiest conflicts of the past three decades. She wore a black eye-patch after losing an eye in a grenade blast reporting on Sri Lanka's civil war in 2001.

ABC/AFP