Attacks come after repeated violations of a truce reached in March last year.
Syrian government artillery shells struck a rebel-held town near the border with Turkey on Saturday, killing four people and wounding more than a dozen.
The Britain-based Syrian Observatory for Human Rights said three policemen, whose station received a direct hit, were among the victims of the attack in the town of Sarmada, in Idlib governorate. At least 17 people were wounded.
The shelling comes amid increasing tensions in the last rebel stronghold in Syria’s northwest, where a truce reached in March last year has been repeatedly violated in recent weeks.
The truce, negotiated between Turkey – which sides with Syria’s opposition – and Russia – the Syrian government’s main backer – ended a crushing government offensive on northwestern Syria.
The war monitor said the attack was claimed by a group known as Supporters of Abu Bakr al-Siddiq Company, an armed group that has claimed previous attacks on Turkish forces.
The area is the last rebel enclave in the country and is home to hundreds of thousands of displaced people.
Syria’s government has pledged to restore control over the territory lost during the 10-year conflict, which began in March 2011.
The army stepped up its bombing of the northwestern enclave when President Bashar al-Assad took the oath of office for a new term on July 17.
As al-Assad took the oath and pledged to make “liberating those parts of the homeland that still need to be” one of his top priorities, attacks on the Idlib villages of Sarja and Ehsin killed 14 civilians, seven of them children.
The following week, Syrian government artillery shells struck the village of Ibleen, killing seven members of the same family, including four children.
SOURCE: AL JAZEERA AND NEWS AGENCIES