Sunday Times journalist Marie Colvin was killed after defying an order to leave the besieged Syrian city of Homs because she wanted to finish "one more story", her mother said tonight.
The award-winning war reporter, 56, died alongside French photojournalist Remi Ochlik, 28, when the house where they were staying was shelled by Syrian government forces this morning.
Fellow journalists mourned the loss of US-born Ms Colvin, highlighting her huge courage in repeatedly placing herself in danger to bear witness to atrocities around the globe.
Her mother Rosemarie said she remained in Homs despite being ordered to get out by her editor because of the risk, adding: "She had to stay. She wanted to finish one more story."
Rupert Murdoch, owner of the Sunday Times, said she was "one of the most outstanding foreign correspondents of her generation".
Ms Colvin was the only British newspaper reporter in the opposition stronghold of Homs, which has become a symbol of the 11-month uprising against Syrian president Bashar Assad.
Syrian activists accused Assad's forces of deliberately targeting the journalists in today's rocket and shell attacks on the city, which they said killed at least 13 people.
The United Nations estimated last month that at least 5,400 people, mostly civilians, had been killed in the Syrian government's crackdown on the rebels.
French politicians expressed outrage at the journalists' deaths. President Nicolas Sarkozy said: "That's enough now, the regime must go."
In Britain, David Cameron joined tributes to Ms Colvin, telling MPs at Prime Minister's Questions: "This is a desperately sad reminder of the risks that journalists take to inform the world of what is happening and the dreadful events in Syria."
Foreign Secretary William Hague said she embodied the "highest values of journalism" and for many years "shone a light on stories that others could not".
He added: "Marie and Remi died bringing us the truth about what is happening to the people of Homs.
"Governments around the world have the responsibility to act upon that truth - and to redouble our efforts to stop the Assad regime's despicable campaign of terror in Syria."
In her final dispatches, Ms Colvin sought to alert the world to the human tragedy unfolding in Homs, which has been devastated after weeks of intense shelling from Assad's forces.
She and Mr Conroy sneaked into the city from Lebanon via a secret smugglers' route despite the risks they faced.
In an interview with the BBC yesterday, she described watching a two-year-old boy who had been hit by shrapnel die in a makeshift clinic.
She said: "The doctor just said 'I can't do anything'. His little tummy just kept heaving until he died. That is happening over and over and over.
"No-one here can understand how the international community can let this happen, particularly when we have an example of Srebrenica - shelling of a city, lots of investigations by the United Nations after that massacre, lots of vows to never let it happen again."
Describing the situation in Homs as "absolutely sickening", she said: "There's just shells, rockets and tank fire pouring into civilian areas of this city, and it's just unrelenting."
In a front-page article published in the Sunday Times at the weekend, Ms Colvin reported that wounded civilians in the Baba Amr area of Homs were being treated by a vet because no doctors were available.
Warning of an impending massacre, she wrote: "The scale of human tragedy in the city is immense.
"The inhabitants are living in terror.
"Almost every family seems to have suffered the death or injury of a loved one."
Ms Colvin was intensely aware of the danger she was in, writing to a friend on Facebook shortly before her death: "I think reports of my survival may be exaggerated.
"In Baba Amr. Sickening, cannot understand how the world can stand by and I should be hardened by now."
The Sunday Times said it was doing all it could to rescue Mr Conroy and recover Ms Colvin's body.
Over her distinguished career, Ms Colvin, originally from Oyster Bay, New York, reported on conflicts around the world, including in Kosovo, Chechnya and Sierra Leone.
She wore a distinctive black eyepatch after losing an eye when she was wounded by shrapnel while covering Sri Lanka's civil war in 2001.
Her recent reporting focused on countries caught up in the uprisings of the Arab Spring, among them Tunisia, Egypt and Libya.
Ms Colvin summarised the foreign correspondent's job succinctly when she addressed a November 2010 memorial service at St Bride's Church in London's Fleet Street for British journalists killed reporting on conflicts.
"Our mission is to report these horrors of war with accuracy and without prejudice," she said.
"We always have to ask ourselves whether the level of risk is worth the story. What is bravery, and what is bravado?
"Journalists covering combat shoulder great responsibilities and face difficult choices. Sometimes they pay the ultimate price."
She added: "It has never been more dangerous to be a war correspondent, because the journalist in the combat zone has become a prime target."
Sunday Times editor John Witherow said Ms Colvin was an "extraordinary figure" in the life of the paper.
He went on: "She believed profoundly that reporting could curtail the excesses of brutal regimes and make the international community take notice.
"Above all, as we saw in her powerful report last weekend, her thoughts were with the victims of violence.
"Throughout her long career she took risks to fulfil this goal, including being badly injured in Sri Lanka. Nothing seemed to deter her.
"But she was much more than a war reporter. She was a woman with a tremendous joie de vivre, full of humour and mischief and surrounded by a large circle of friends, all of whom feared the consequences of her bravery."
ITV News international editor Bill Neely added: "At a time when journalists are being examined as never before, it's time to acknowledge someone who made a difference, a moral difference, to our country and our lives. That was Marie."
A number of Western journalists have died in Syria since the uprising began.
French TV reporter Gilles Jacquier, 43, was killed in Homs last month, and New York Times correspondent Anthony Shadid, also 43, died of an apparent asthma attack last Thursday as he was leaving Syria.
Jim Boumelha, president of the International Federation of Journalists, warned: "The situation in Homs is becoming increasingly difficult for journalists and we are concerned about its impact on independent reporting on the conflict.
"We will hold the authorities to their international obligations to protect journalists who are in Homs and other Syrian cities."
Foreign Office officials told Syrian Ambassador to London, Dr Sami Khiyami, the UK Government was "horrified" by the violence in Homs and expects immediate arrangements to be put in place for Ms Colvin's body to be repatriated.
Mr Hague ordered officials to summon Syria's representative to a meeting with political director Sir Geoffrey Adams this afternoon.
A Foreign Office spokesman said: "The political director said the Foreign Office expected the Syrian authorities to facilitate immediate arrangements for the repatriation of the journalists' bodies, and for the medical treatment of the British journalist injured in the same attack.
"Sir Geoffrey stressed that the British Government was horrified by the continuing unacceptable violence in Homs, which has been under attack for 19 days.
"He noted that today alone the world had witnessed the death of more than 60 civilians, including children, on the single street of al-Hakoura in the Baba Amr neighbourhood.
"Our clear demand was for the violence to stop immediately. The Syrian authorities must implement the undertakings they had given to the Arab League, halt all violence against civilians, and start an orderly political transition before a single further death took place."