A ceasefire in northwest Syria, part of a wider deal that included cessation of hostilities in the area, as well as in a town near the Lebanese border, has been broken after just one day, according to an activist monitoring group.

Shells apparently fired by rebel fighters hit the village of Fuaa in the province of Idlib on Saturday, the UK-based Syrian Observatory for Human Rights has said, after rebels blamed government forces for violating the ceasefire by dropping barrel bombs on an area nearby.

Warring sides, including Hezbollah, had agreed on Friday a ceasefire in Fuaa and next-door Kafraya, two villages held by pro-government forces and besieged by rebels, as well as in the town of Zabadani near the Lebanese border, where fighters are holed up and surrounded by government forces.

But shelling of Fuaa resumed, the observatory said, with no immediate casualties reported.

The shelling came after an online statement purportedly from fighters in the area blamed the government for violating the ceasefire by dropping barrel bombs on the nearby village of Taftanaz.

The statement said fighters retaliated by firing at Fuaa and Kefraya.

The observatory said explosions had been heard in Taftanaz, with activists blaming government barrel bombs for killing at least five people there.

Hassan Nasrallah, the leader of the Lebanese Shia group Hezbollah, which backs Syrian government forces, had confirmed on Friday that a long-term ceasefire deal had been reached which would include the withdrawal of rebel fighters from Zabadani in exchange for the evacuation of civilians from Fuaa and Kefraya.

The deal had been reached in talks backed by Iran.