Journalist Marie Colvin, photographed in Tahrir Square in Cairo, in an undated photo made available in February 2012. (Ivor Prickett/Sunday Times via Associated Press)

American war correspondent Marie Colvin was deliberately targeted and killed by artillery fire in 2012 at the direction of senior Syrian military officers seeking to silence her reporting on civilian casualties in the besieged city of Homs, according to a civil lawsuit filed Saturday on behalf of her sister and other heirs.

Based on information from high-level defectors and captured government documents, the 32-page complaint alleges that the military was able to electronically intercept Colvin’s communications from a clandestine media center operating out of an apartment in the densely populated Baba Amr neighborhood in Homs. Syrian officials paired the intercepts with detailed information from a female informant to pinpoint the location of the reporter who worked for the Sunday Times of London.

Then, the suits says, military forces under the direction of President Bashar al-Assad’s brother, Maher, commander of Syrian army’s 4th Armored Division, launched a series of “bracketing” artillery attacks that came progressively closer to the media center, a classic artillery targeting tactic.

Colvin, 56, and French photographer Remi Ochlik, 28, were killed instantly after a shell landed outside the front door as they reached the bottom step of stairs leading to the foyer while trying to flee. Two other foreign journalists, including Times photographer Paul Conroy, were severely injured but later escaped.

The assault, the suit states, was part of a coordinated Syrian campaign developed in late 2011 to impose a media blackout on the war by killing and apprehending professional and citizen journalists whose work was reaching worldwide audiences.

In this Feb. 22, 2012, citizen journalism image, flames rise from a house from Syrian government shelling in the Baba Amr neighborhood of Homs province. (Local Coordination Committees in Syria/Associated Press)

An undated photo of French photographer Remi Ochlik as he was covering the Tunisian revolution. Ochlik died Feb. 22, 2012, in Homs, Syria. (Yoan Valat/Associated Press)

Filed in U.S. District Court for the District of Columbia, the lawsuit asserts that Colvin was under surveillance by intelligence sources while she was in Lebanon preparing to sneak into Syria. A plan to kill her and other foreign journalists was formulated by the high-level Central Crisis Management Cell that Assad had charged with tracking and destroying opponents of his rule.

The plan was executed by the Homs units of the Syrian Republican Guard and Special Forces working with a paramilitary death squad known as the shabiha, Arabic for ghosts, the lawsuit asserts.

The complaint names nine military officers and Khaled al-Fares, the death-squad leader, as responsible for executing the extrajudicial killing of civilians, a violation of the Foreign Sovereign Immunities Act and the international law of armed conflict, which considers it a war crime to deliberately kill civilians during war.

Maher Assad gave Fares a black luxury vehicle as a reward for the killing of Colvin and Ochlik, the lawsuit asserts.

“The thought that she was being watched the whole time, and she didn’t know it, is chilling,” said Cathleen Colvin, her sister and the lead plaintiff. “I feel really strongly that Marie was silenced, and I can’t let that stand without bringing her killers to justice. I’m sure if the roles were reversed, she would do the same and more.”

Colvin, a native of New York, spent 26 years in war zones on three continents, drawn to the plight of war’s civilian victims. Her bravery was legendary. In the 1991 Iraq War, she stayed behind enemy lines. In 1999, when others fled, she remained in East Timor to document the 1,000 refugees in a U.N. compound under attack by government-backed militias.

In 2001, she was blinded in one eye by the blast of a Sri Lankan army rocket-propelled grenade. Her black eye patch symbolized her fearlessness and commitment to telling the stories of civilians who, she reminded her worried friends and readers, “endure far more than I ever will” and cannot escape to the comforts of London, where she lived.

When others at the media center wanted to leave Syria, Colvin would not budge, recalled Javier Espinoza, a Spanish journalist who survived the attack, in an interview. “Marie wanted to stay in Baba Amr,” he said. “She said it was her duty.”

Journalist Marie Colvin, second from left, poses for a photograph with Libyan rebels in Misurata in this June 4, 2011, file photograph. (Zohra Bensemra/Reuters)

At least 100 journalists, most of them Syrian, have been killed since war broke out in 2011, according to press advocacy groups. Many others have been detained or kidnapped. Among them is American freelancer Austin Tice, a former Marine who was kidnapped six months after Colvin’s death. The Syrian government has never acknowledged detaining Tice, but U.S. officials think the government or a group affiliated with it is holding him.

The lawsuit against the Syrian government, filed by lawyers from the California-based Center for Justice & Accountability and the Shearman & Sterling firm, draws on insider information from former Syrian government officials and other defectors, some with direct knowledge of the assassination plans, said Scott Gilmore, the lead attorney in the case.

Gilmore said he and others from the Center spent three years tracking down former regime members, informants, citizen journalists and other witnesses to the attack and its planning from among the vast Syrian diaspora that fled the war and entered Europe.

It is the first lawsuit to use as evidence some of the more than 600,000 documents obtained by the Commission for International Justice and Accountability. CIJA is an independent group of war crime investigators and lawyers who have trained and organized Syrian students, researchers, activists and lawyers to find and cart away official documents they hope to use to eventually prosecute Assad and others for war crimes and atrocities during the conflict.

One of the documents, dated Aug. 6, 2011, and reported to be from Syria’s National Security Bureau, instructs provincial commanders to apprehend “those who tarnish the image of Syria in foreign media and international organizations.”

The Colvin case is likely to take years to wind through the courts, Gilmore said. But even if the Syrian government never answers the charges, a judge can still rule in the matter. The U.S. government holds millions of dollars in frozen Syrian assets which a court could use as restitution, Gilmore said.

“I can assure you that this is false by all standards and is certainly not true,” said Mohammed Ramez Turgeman, the Syrian minister of information, in a brief phone interview.

The suit seeks unspecified punitive damages for the intentional infliction of emotional distress to Colvin’s family and others. “The Assad regime’s assassination of Marie Colvin,” it says, “was designed to intimidate and terrorize the civilian population of Syria, the victim’s loved ones, other journalists, and the international community.”

Last month, in a case also brought by the Center for Justice & Accountability, a civil jury in Orlando found former Chilean army officer Pedro Pablo Barrientos Nuñez liable for the 1973 murder of singer and activist Victor Jara. It awarded Jara’s widow and daughters $28 million.

The Colvin lawsuit lays out a detailed chain of events that led to her killing in Baba Amr, the epicenter of opposition activity. “Silencing journalists was central to the Assad regime’s strategy to crush political opposition,” it says.

Prominent freelancers, citizen journalists and cartoonists began to be arrested or killed in late 2011. Intelligence branches received instructions to target media critics and wanted lists were distributed, the lawsuit says. Rewards were offered for the capture of any foreign journalist.

In January 2012, high-ranking Syrian officials met with Arab League monitors and demanded to know where they had met journalists during their visit. They accused reporters associated with the media center of being terrorists, denounced The Washington Post and the New York Times as “terrorist newspapers” and accused foreign journalists of being spies, the lawsuit states in a chronology of events.

Deputy Defense Minister Assef Shawkat told the monitors “he could destroy Baba Amr in ten minutes . . . if there were no cameras,” according to the lawsuit.

At around the same time, intelligence sources in Lebanon were reporting that teams from CNN, the BBC and the Sunday Times were being smuggled into Homs, it said. The Computer and Signals Section of Military Intelligence Branch 261 swung into action. It used intercept devices to monitor satellite-dish and cellphone communication to trace journalists’ location.

By then, regime officials monitoring the news had ordered forces to recruit more informants to help find journalists. Shelling intensified, lasting from dawn to nightfall.

Conroy, the Times photographer accompanying Colvin, said he thinks her lengthy broadcasts with the BBC and CNN the night before she was killed were intercepted by authorities. “That’s when everything came together,” he said.

During those broadcasts, Colvin described watching a 2-year-old die of shrapnel wounds. Conroy’s footage captured the child’s passing.

From the small apartment building turned media center, whose top floor had been blown off by munitions, Colvin told CNN that the regime’s contention it was only targeting combatants was “a complete and utter lie. . . . the Syrian army is simply shelling a city of cold and starving civilians.”

In the early morning of Feb. 22, the female informant was debriefed by commanders and then shown aerial footage and maps of Homs. She identified the media center, which was then matched to the location of the intercepted broadcast signals, the suit says.

When Conroy, a former British artillery target locator, heard the distinct pattern of artillery shells getting closer and closer to the center later that morning, “I immediately sensed something was different,” he said. “That’s when I got spooked.”

“It was the first time I’d really seen them acting like a professional military,” Conroy said in an interview from London. “Once they got the building, they stayed on it. I realize how lucky we were for anyone to get out of the building alive.”

Suzan Haidamous in Beirut contributed to this report.