At least 12 civilians were killed and dozens wounded on Wednesday during shelling by Syrian government forces of a neighborhood in the central city of Hama, a monitoring group said.
The Syrian Observatory for Human Rights said the victims died in the city's Mashaa al-Tayaran district.
The shelling occurred despite a declared ceasefire that technically went into effect on April 12 and the presence in Hama of two UN observers monitoring the truce.
A video posted on YouTube by activists following the shelling showed what appeared to be several houses reduced to rubble and people digging with their bare hands to search for survivors.
A large crater could also be seen.
"The shelling took place at 6:15 p.m. [1513 GMT] and led to the destruction of many houses," said Abu Ghazi, a local activist reached through the voice-over-Internet Protocol service Skype. "Many victims remain under the rubble."
He described Mashaa al-Tayran as a working class neighborhood.
A local resident reached by AFP described the situation as "very dramatic" and said the death toll was likely to rise.
More than 300 people have been killed in violence across Syria since the two-week ceasefire brokered by UN-Arab League envoy Kofi Annan.
An advance team of UN observers has been in Syria monitoring the truce since April 15 and has visited several flashpoint towns. Two of the observers, set to number 30 by the end of the week, have set up base in Hama.
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