Three people were killed in the Khan Sheikhoun district of Idlib, and one in Latmeen village in Hama's countryside, sources said.
A brief truce announced by the regime last Thursday, but it resumed military airstrikes on Idlib province on Monday. The regime accused opposition groups of targeting an airbase of its ally, Russia, and scrapped the cease-fire in the region.
The first meeting of the Astana process was held in Turkey in January 2017 to bring all warring parties in the Syrian conflict to the table to facilitate U.N.-sponsored peace talks in Geneva. The Astana talks support the establishment of the U.N.-backed constitutional committee in Syria as a part to find a political solution.
Last year, the Sochi agreement was reached on Sept. 17 by President Recep Tayyip Erdoğan and his Russian counterpart Vladimir Putin. According to the agreement, the cease-fire in the Idlib region will be preserved, with the withdrawal of heavy arms and radicals from the region. However, even though the region of Idlib was declared a de-escalation zone, the attacks of the Syrian regime and Russia continued unceasingly on the last opposition stronghold, leading to deaths as well as the displacement of hundreds of thousands of people.
The de-escalation zone is currently inhabited by about 4 million civilians, including hundreds of thousands of people displaced by the regime forces from cities and towns throughout the war-weary country in recent years.
Syria has been locked in a vicious civil war since early 2011, when the Bashar Assad regime cracked down on pro-democracy protests with unexpected ferocity.
Since then, hundreds of thousands of people have been killed and more than 10 million others displaced, according to U.N. officials.