(Adds report from activist and context)
BEIRUT, Jan 18 (Reuters) - A large blast hit a neighbourhood of the Syrian city of Aleppo on Friday and caused several casualties, state television said.
It was unclear who was behind the attack.
Syria TV said the explosion had been caused by a rocket fired by a "terrorist group" - a term it frequently uses to describe rebels in the 22-month-old uprising against President Bashar al-Assad.
But opposition groups said Assad's forces were behind the blast, which hit the Muhafaza Sakaniya neighbourhood in a western district of the city.
Video from state television showed the side of a building collapsed into rubble that spilled into nearby streets. A crowd sifted through the wreckage as medics pulled bloodied bodies onto stretchers.
Activists said the district, a government-held area of a city that has descended into a long and bloody stalemate between army and rebels, had been hit by a military air strike.
"The rebels do not have this capability yet," said Hameed Barrasho, an activist in Aleppo speaking by Skype. "We have several reports of a jet in the area before the strike. This is the regime trying to sow more chaos in the city."
Syria's government restricts foreign media access to parts of the country it holds, making it difficult to confirm accounts by either side.
Earlier in the week, twin blasts at the University of Aleppo killed more than 80 people. Each side blamed the other.
(Writing by Alexander Dziadosz; Editing by Kevin Liffey)