Syrian jihadists and allied rebels seized a key town from government forces on Tuesday in a new offensive in the central province of Hama, a monitor and fighting factions said.
The surprise offensive was announced Tuesday by the Tahrir al-Sham alliance, which is dominated by the jihadist Fateh al-Sham Front, once linked to Al-Qaeda.
"This afternoon, Tahrir al-Sham began preparing for military operations against (regime) army positions in Hama province," said Tahrir al-Sham press officer Imad al-Din Mujahid.
Tahrir al-Sham published photos of a massive explosion that it said was a suicide attack against a government checkpoint inside Suran.
Hama province is of strategic importance to President Bashar al-Assad, separating opposition forces in Idlib from Damascus to the south and the regime's coastal heartlands to the west.
"Tahrir al-Sham detonated two car bombs as they stormed the town of Suran and other villages," said Rami Abdel Rahman, head of the Syrian Observatory for Human Rights.
The British-based monitor said the jihadists and rebel groups seized Suran and eight surrounding checkpoints within hours, despite heavy air strikes by government warplanes.
The town has exchanged hands several times in Syria's six-year conflict, with government forces recapturing it in late October from opposition factions.
The Free Idlib Army, which is taking part in the offensive, said it targeted the Hama military airport and other government positions on Tuesday.
Rebel groups and Tahrir al-Sham were also waging an offensive in Syrian capital on Tuesday in a bid to link two neighbourhoods they control in Damascus.
The violence comes two days before UN-brokered peace talks are set to resume in Switzerland between government officials and opposition representatives.
Syria's conflict erupted in March 2011 with protests against Assad's rule, but has evolved over the years into a complex civil war.
More than 320,000 people have been killed and millions more displaced by the conflict.