A UN human rights probe found on Thursday that Syria had "manifestly failed" to protect its own people as a defiant regime brushed off an outcry over the killing of two journalists, saying they had entered illegally and at their own risk.
Activists spoke of "terrifying explosions" in the flashpoint central city of Homs where veteran American reporter Marie Colvin and French photojournalist Remi Ochlik were killed as encircling regime troops pounded rebel neighbourhoods for a 20th straight day.
The international investigators said in their report that they had submitted a list of Syrian military and political officials suspected of crimes against humanity to the UN's top human rights official.
"The commission has deposited with the High Commissioner (for Human Rights, Navi Pillay) a comprehensive database containing all evidence collected," the international commission of inquiry said.
"Consistent with its mandate, the commission endeavoured, where possible, to identify those responsible with a view to ensuring that perpetrators of violations, including those that may constitute crimes against humanity, are held accountable," added the inquiry, commissioned by the UN Human Rights Council.
The commission documented a widespread and systematic pattern of gross violations committed by Syrian forces, "in conditions of impunity," since March 2011 when the uprising against President Bashar al-Assad's regime erupted.
The report said the Syrian government had "manifestly failed" to protect its people, but also said that it had found instances of gross abuses committed by rebel fighters, many of whom are mutinous soldiers.
The commission recommended the initiation of an inclusive political dialogue, bringing together the government and opposition groups.
Both sides should "negotiate an end to the violence, to ensure respect for human rights and to address the legitimate demands of the Syrian people," it said.
According to the British-based Syrian Observatory for Human Rights, more than 7,600 have been killed in the 11 months since the uprising began.
Nine people, including five soldiers, were killed on Thursday, the Observatory and state media said.
The dawn bombardment of Homs -- Syria's third-largest city -- centred on the Baba Amr neighbourhood, where the two journalists were killed, a human rights watchdog said.
"Baba Amr, as well as parts of Inshaat, have been shelled since 7:00 am (0500 GMT), while mortar rounds slammed into the Khaldiyeh neighbourhood," the watchdog's head, Rami Abdel Rahman, said.
Activist Hadi Abdullah told AFP from inside the city: "We hear terrifying explosions."
He said the world outcry over the deaths of the journalists and 24 Syrian civilians in Homs on Wednesday appeared only to have strengthened the regime's determination to eliminate all opposition in the city.
"The more the condemnations pile on, the heavier the bombing becomes," he said.
Signup to our newsletter and follow us on Facebook and Twitter!
Abdullah said there was evidence that the makeshift media centre where the journalists were killed and two others wounded was deliberately targeted by regime forces.
"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."
The Syrian government made no denial that its forces had fired the lethal rounds.
"We reject statements holding Syria responsible for the deaths of journalists who sneaked into its territory at their own risk," said a foreign ministry statement read out on state television.
The ministry urged journalists to "respect laws of journalistic work in Syria and avoid breaking the law by entering the country illegally to reach trouble-hit areas that are unsafe."
Rupert Murdoch, who owns The Sunday Times for which Colvin worked, said one of the paper's photojournalists, Paul Conroy, was also wounded.
French newspaper Le Figaro said one of its reporters, Edith Bouvier, was wounded in the legs when the press centre was hit.
The paper said it was trying to contact her amid concerns that she needs surgery.
It said it had talked to Bouvier on Wednesday, when a video surfaced on the Internet showing her conscious and responsive but with bandaged legs.
Bouvier needs surgery because of displaced fractures, said a Le Figaro executive, who has been in touch with the foreign ministry and the Red Cross to coordinate an evacuation.
"Because the bombings are particularly intense, no one has been able to climb to the roof to use a satellite phone," said a spokesman for the global press watchdog Reporters Without Borders.
Washington accused Damascus of "shameless brutality" in its bombardment of the makeshift press centre, while Paris held the regime responsible.
British Foreign Secretary William Hague said he would push for a tightening of the diplomatic and economic "stranglehold" on Syria at a meeting of regional powers in Tunisia on Friday.
He said he would hold preparatory talks Arab and Western counterparts later on Thursday on the sidelines of a major conference on Somalia in London.
"I will be discussing today with (US Secretary of State) Hillary Clinton and many of the Arab leaders what we can achieve at that meeting (in Tunisia). I think part of that has to be tightening a diplomatic and economic stranglehold on the Assad regime," he told the BBC.