The Syrian government has denied responsibility for the deaths of the two foreign journalists killed in Homs, as British Foreign Secretary William Hague ruled out the possibility of military intervention, Sky News reported.

The Syrian foreign ministry said Marie Colvin and Remi Ochlik, who were killed when a rocket struck the makeshift media centre in which they were staying, "sneaked" into the country, and were there illegally.

"We reject statements holding Syria responsible for the deaths of journalists who sneaked into its territory at their own risk," said a ministry statement read out on state television.

Activist Hadi Abdullah, a member of the General Commission of the Syrian Revolution, said it was clear the government was responsible.

"We are sure that the centre was targeted, because 11 rockets struck in and around it," he said. "The regime forces intercepted a transmission signal," he added.

Following the denial, the UN announced that Syria had committed crimes against humanity under orders from "the highest levels" of the army and government.

The UN said the report also includes a confidential list of commanding officers and senior officials who appear responsible for international crimes.