Syrian government forces have recaptured a village in central Hama province, Syria's state news agency reported, as activists say 17 were killed barrel bombs in northwest Daraa.
The violence comes a day after the Free Syrian Army rebel group fired and replaced its military chief, Salim Idriss.
State news agency SANA, quoting a military source on Monday, said "army units have established total control over Maan, after crushing the terrorists who had infiltrated (the village) and committed a massacre against its civilian residents, killing dozens of them, including women".
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State television also reported the army's recapture of Maan, saying 42 civilians had been killed by "terrorists".
Also on Monday, 17 people were killed and dozens injured after a government aerial bombardment using explosive barrels targeted the town of Muzayrib in northwest Deraa according to local activists.
In central Hama province, activists said bombing by helicopter gunships took place in the town of Kafr Zeita.
Footage uploaded to the internet by activist groups showed what they claimed was a missile attack on a tank by the Tawheed Brigade, who operate in and around Aleppo.
Shelling was also reported in the eastern Ghouta on the outskirts of Damascus, in the town of Mleiha. An activist video showed the rubble-lined streets after what they said was a shelling attack.
In the Qalamun Mountains near Damascus, shelling resumed on key rebel bastion Yabrud, which has been under fire since Friday from government troops.
In the northern Aleppo province, Alaa Jabbu, the head of the rebel Kurdish Front, was killed in army shelling according to AFP news agency.
The Syrian Observatory for Human Rights reported that a man of German origin was killed alongside other fighters in a bomb blast in the rebel-held town of Minjeb in the northern Aleppo province.
Free Syria Army chief fired
The Free Syrian Army fired Salim Idriss as its military chief, calling him "ineffective" and lacking in experience to lead military operations on the ground.
In a video broadcast on the internet on Sunday, the rebel coalition said its military council had decided to replace Idriss with Brigadier General Abdel-illah Albashir.
Colonel Qassem Saadeddine said the decision was taken due to "the paralysis within the military command these past months".
A source inside the Syrian opposition told AFP news agency that Idriss, who was appointed to the role in December 2012, had faced criticism for failings on the battlefield.
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Al Jazeera's Omar Al Saleh, reporting from Istanbul, said the Supreme Military Council said Idriss was "ineffective" and "lacked the military experience to run operations on the ground".
"Combined with the failure of the Geneva talks, the head of the Syrian National Coalition returned to Syria and promised rebels in Idlib that they would soon be receiving more weapons and support," our correspondent said.
This restructuring is intended to raise morale among the FSA, once the country's strongest armed opposition force but has been weakened by internal rifts and by competition from other rebel coalitions.
In December, the US and Britain suspended non-lethal aid to the FSA, dealing a major blow to a group that appears caught between advancing regime forces and the increasingly unified Islamic Front.