The Government has told Syrian officials it is "horrified" by the ongoing violence in Homs following the death of Sunday Times journalist Marie Colvin, who was killed during a shell attack in the besieged city.

Syrian Ambassador to London, Dr Sami Khiyami, was summoned to a meeting with senior Foreign Office officials after the award-winning war reporter, 56, was found dead in a house targeted by government forces.

Diplomats demanded immediate arrangements be put in place to repatriate Ms Colvin's body and for the medical treatment of Sunday Times photographer Paul Conroy, who was injured in the attack.

FCO political director Sir Geoffrey Adams met with the Syrian representative and "stressed that the British Government was horrified by the continuing unacceptable violence in Homs, which has been under attack for 19 days", a department spokesman said.

The FCO spokesman added: "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."

US-born Ms Colvin was killed after defying an order from her editor to leave the opposition stronghold of Homs because she wanted to finish "one more story", her mother Rosemarie said. She was the only British newspaper reporter in the city, which has become a symbol of the 11-month uprising against Syrian president Bashar Assad.

French photojournalist Remi Ochlik, 28, also died in the attack while French reporter Edith Bouvier, of Le Figaro newspaper, was seriously injured.

Fellow journalists mourned the loss of Ms Colvin, highlighting her huge courage in repeatedly placing herself in danger to bear witness to atrocities around the globe. Sunday Times owner Rupert Murdoch described her as "one of the most outstanding foreign correspondents of her generation".

David Cameron joined the tributes saying the tragedy was "a desperately sad reminder of the risks that journalists take to inform the world of what is happening and the dreadful events in Syria". Meanwhile, Foreign Secretary William Hague said Ms Colvin embodied the "highest values of journalism" and for many years "shone a light on stories that others could not".

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.