Clandestine monitors inside Syria say dozens died in Latamneh, a suburb of the city of Hama, as a result of government shelling.
Video said to be from Homs showed 13 victims of an apparent mass execution.
UN chief Ban Ki-moon has warned the government not to use the impending truce as an "excuse for killing".
Turkey says refugee arrivals from Syria have doubled since President Bashar al-Assad agreed to implement a peace plan from the UN and Arab League.
Scepticism
The six-point plan, mediated by former UN chief Kofi Annan, envisages a cessation of armed violence by all parties from 10 April, with a full ceasefire on 12 April.
However, the Syrian opposition, the US and many countries in the region have expressed scepticism that Syria is committed to the plan.
The Oranisation of Islamic Co-operation, has pledged to raise $70m (£44m) to help about one million people in need in Syria.
The OIC said it had received permission from Damascus to send aid.
In Damascus on Saturday, thousands of supporters of Mr Assad attended a rally to mark the 65th anniversary of the ruling Baath Party.
A death toll of 107 - including 74 civilians - was reported by the Syrian Observatory for Human Rights, based in London.
Another monitoring group, the Local Co-ordination Committees, gave a figure of 133, not including members of the Syrian security forces.
