Bomb attacks killed at least 28 people in Syria's second city Aleppo Friday, while Homs endured another day of shelling and a firefight broke out in Damascus, the nearest violence to the centre of the capital in an 11-month uprising.
The two Aleppo bombings were the worst violence to hit the country's commercial hub during the revolt against the Assad family's 42-year dynastic rule.
Mangled bodies and severed limbs lay on the pavement outside the military and security service buildings that were targeted - as shown in live footage on Syrian television, which has consistently portrayed the revolt against President Bashar al-Assad as the work of foreign-backed terrorists.
No one claimed responsibility for the Aleppo bombings but they took place as Assad's forces grow more ferocious in operations to crush the uprising. Some opposition figures accused the government of manipulating events to discredit them.
Friday saw more unrest across the country, with activists reporting that security forces opened fire in Latakia, in the town of Dael in Deraa province, and elsewhere to break up demonstrations taking place after weekly Muslim prayers.
In Damascus, members of the Free Syrian Army fought for four hours with troops backed by armoured vehicles who had entered al-Qaboun neighbourhood in the north of the capital during a protest one mile from the main Abbaside Square, activists said.
The rebels said they had sustained several casualties but it was not known if any had died of their wounds.
In a troubling sign of how sectarian tensions could spill across the region, at least one person was wounded in gunfire and grenade blasts in the Lebanese city of Tripoli, where Sunni Muslim and Alawite communities are divided on the fate of Assad.
In the western Syrian city of Homs, where a week of bombardments has killed dozens of civilians and drawn condemnation from world leaders, four people were killed in the opposition-held neighbourhoods of Baba Amro and Bab Sebaa, the activist Syrian Observatory for Human Rights said.
Troops also opened fire as worshippers left a mosque in Homs after Friday prayers.
Activists in Homs said shelling started up again in the morning and they feared a big push was imminent to storm residential areas of the city that has come to symbolise the plight of those opposing the Assad government.
The carnage in Homs continues and the martyrdom of the Syrian people continues, French Foreign Ministry spokesman Bernard Valero said. Not only are we seeing an army that is massacring its own people, but for the Syrian army hospitals and doctors have become systematic targets for repression.
But the unrelenting violence only highlighted the difficulties that Western and Arab powers faced in trying to resolve the crisis in a country with a well-armed military and a key place in the Middle East's precarious strategic balance.
Bolstered by Russian support, Assad has ignored appeals from the United States, Turkey, Europeans, fellow Arabs and other governments to halt the repression and to step down.
Foreign ministers of the Arab League, which suspended a monitoring mission in Syria last month because of the violence, will discuss a proposal to send a joint U.N.-Arab mission to Syria when they meet in Cairo Sunday, a League official said.
French Foreign Minister Alain Juppe will meet his Russian counterpart in Vienna Thursday to discuss Syria, Valero said.
The European Union's foreign policy chief, Catherine Ashton, added her voice to international calls for Moscow, Syria's strongest ally and main arms supplier, to support a United Nations resolution demanding Assad halt the crackdown.
Saudi Arabia's King Abdullah also offered criticism of the Russian and Chinese veto of the resolution - something unlikely to impress Moscow, which cites Western backing for him and other Gulf monarchs as proof of double standards when Washington and European governments condemn authoritarian leaders.
Saudi Arabia circulated a draft resolution backing an Arab peace plan among members of the U.N. General Assembly Friday which, like the failed council resolution, fully supports the last month's Arab League plan, diplomats said.
Russia, which has sent tanks into its own rebel cities in recent memory and is keen to counter U.S. influence in the region, says no one should interfere in Syria's affairs.
Deputy Foreign Minister Sergei Ryabkov, accusing unspecified
Western states of arming the rebels and giving them advice, said on Friday: The U.N. Council is not a tool for intervention in internal affairs and is not the agency to decide which government is to be next in one country or another.
If our foreign partners don't understand that, we will have to use drastic measures to return them to real grounds.
In Geneva, the United Nations human rights office took a different view, highlighting universal human rights law as grounds for reminding Syrian officials that those suspected of committing or ordering crimes against humanity should face prosecution in the International Criminal Court.
This would give a very, very strong message to those running the show, Rupert Colville, spokesman for U.N. High Commissioner for Human Rights Navi Pillay, said.
Pillay will address a U.N. General Assembly session on Syria being held in New York Monday, Colville said.
Officials from the United States and other nations have raised the possibility of a humanitarian operation to help the people of Homs, but diplomats said establishing safe corridors would be fraught with risk and difficulty.
And having ruled out intervening militarily, as NATO did decisively in Libya nearly a year ago, the foreign powers arrayed against Assad have few good cards to play.
Assad can count on the powerful military and a certain degree of popular support to survive, and the leadership of the revolt is fragmented.
The Aleppo blasts played into the government narrative that it is only defending the state against violent foes.
In a live television report, a correspondent lifted blankets and plastic sheets which had been laid over corpses on the pavement to show a body with its head blown off. Other bloodied human remains included a limbless torso and a severed foot.
We apologise for showing these pictures, but this is the terrorism which is targeting us, the reporter said.
State television said 28 people were killed and 235 wounded in the blasts at a military building and a security forces base.
A concrete wall around one building was badly damaged and its windows were blown out. The TV reporter said children were among the dead, showing a roller skate left on the pavement.
Meanwhile in besieged Homs, activists said shelling began again in the morning and outgunned rebels loosely grouped under the Free Syrian Army were expecting an onslaught.
In a message of defiance during the overnight lull, activists staged a rally against Assad in the Homs neighbourhood of al-Bayada. YouTube footage showed hundreds of youths holding hands and dancing to the tune of a songs chanted by Abdelbasset Sarout, a 22-year-old soccer star turned activist.
You oppressor, go ... Great Homs, Syria will be free, Sarout sang from a makeshift stage while white and green rebel flags fluttered overhead.
Activist Mohammad Hassan said the respite in the shelling had allowed him to leave his basement and survey the extent of the damage: There isn't one street without two buildings or more that are badly damaged from the shelling, he said by satellite phone.
Makeshift hospitals in Homs have been struggling to cope with the casualties from the government bombardments and sniper fire, and medical supplies and food are running out.
The deputy head of the International Committee of the Red Cross, Laurent Fellay, told Reuters that access to the growing number of casualties in Syria was getting more difficult as the violence intensifies.
The Local Coordination Committees, an opposition group in Homs, put the death toll Thursday alone as high as 110 by nightfall, though it is impossible to verify such accounts.
Bombardments were also brought to bear on the rebel-held city of Zabadani, in the mountains 20 km (15 miles) northwest of Damascus, where clashes took place between government forces and army defectors, the Observatory for Human Rights said.
(Additional reporting by Dominic Evans in Beirut, John Irish in Paris, Stephanie Nebehay in Geneva; Writing by Angus MacSwan in Beirut; Editing by Alastair Macdonald)