AMMAN - Violence flared across Syria, including bomb attacks that killed at least 28 people in Aleppo, while at the United Nations diplomats said a new effort was afoot to gain backing for an Arab peace plan to end 11 months of bloodshed in the country.

  The two Aleppo bombings on Friday were the worst attack to hit the country's commercial hub during the revolt against the 42-year dynastic rule by the family of President Bashar al-Assad.

  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 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 the western 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.