Opposition groups in Syria say a powerful blast has hit the northern city of Aleppo, killing a guard at an office of President Bashar al-Assad's ruling Baath Party, Reuters reported.
It is understood that the blast happened near a car park late Friday night.
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The incident comes after Syrian state television said the army had foiled an attempted suicide attack in Aleppo, Syria's second largest city.
The would-be bomber, who was killed by security forces, had a car filled with 1,200 kilos of explosives, Reuters reported.
Meanwhile British based monitors said one civilian was killed earlier Friday when Syrian security forces opened fire on protesters in Aleppo.
Tens of thousands of people protested in cities across Syria, a day after two bombings killed 55 people in the capital Damascus, Agence France Presse reported.
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11 civilians were reported killed in other cities, including Hama in central Syria, and Daraa in the south.
The Syrian opposition has accused the government of seeking to destroy a UN-Arab League peace plan designed to end 14 months of violence.