Violence continued to rage in Aleppo as well as Damascus on Sunday as clashes between Syrian rebel groups and regime forces tore through the country's two major cities.
Government helicopter gunships and rockets were fired at rebel forces in the Damascus suburb of Barzeh, according to Sky News, while there is also reported to be fierce fighting to the west of the city, in Mezze.
BBC correspondant Jim Muir reported that the less-heavily equipped rebel groups seem to be losing "the straight battle" in the face of the heavily armed government forces.
The regime army has escalated the ferocity of its attacks on Aleppo and Damascus over the past few days. Their offensive has been interpreted as a bid to regain to control by many, after a bomb attack killed four senior regime figures earlier this week.
Rebels have also gained some important strongholds over the past few days, including three frontier posts, according to Sky News.
Brig. Gen. Abdul Kareem al-Ahmad of the rebel Free Syrian Army told a meeting in Turkey that the war was "now being waged in the heart of Syria in Damascus" reported news agency Associated Press.
However as the fighting moves into Syria's more densely populated cities, it is likely that the fatalities of both soldiers and civilans will continue to increase.
The Syrian Humans Rights Observatory recorded 2,752 deaths in July, which has marked the deadliest month since the uprising began. The UK-based group estimates that more than 19,106 people have died since the conflict began.
The Red Cross declared the conflict to have reached a state of civil war, meaning that both sides can now be prosecuted for war crimes if their violence is deemed to break international laws.
Syrians are fleeing the fighting in record numbers, with 30,000 people reported to have crossed the border to Lebanon in the past month, according to UN figures.
Earlier this week four senior figures were killed after a blast at the national security building, an attack described by Channel 4 correspondant Alex Thompson as "the most significant penetration of Syrian government security" since the conflict began.
The casulties including Assad's brother-in-law, Assef Shawkat the man widely regarded as the mastermind behind the government’s brutal crackdown.
Defence minister Daoud Rajiha was also killed after a blast struck the National Security Bureau on Wednesday morning and former defence minister Hasan Turkmani died, while Maher Assad, the president’s brother and the leader of the renowned 4th Armoured Division, reportedly sustained injuries.
Rumours circulated that Assad himself may have been injured in the blast or have fled the capital with his British-born wife Asma, but state TV showed footage of him swearing in a new defence minister.
"I have a very clear message for president Assad. It is time for him to go," said the Prime Minister after the blast earlie rthis week.
However at the UN on Thursday afternoon, Russia and China vetoed a Security Council draft resolution to hit Syria with further sanctions.