Regime air strikes and artillery fire in northwestern Syria, including on schools in the city of Idlib, killed 19 civilians on Tuesday, a war monitor said.
The Syrian Observatory for Human Rights said eight children were among those killed in the raids on Idlib city and the towns of Binnish and Maarat Misrin.
It said schools were hit in Idlib, the main city in the densely populated, ever-shrinking enclave of the same name -- the last major territory in Syria still controlled by rebels and militants.
At least six children were among 10 civilians killed in Maarat Misrin, a town just north of Idlib city on the road to the Turkish border, the Observatory said.
"Among the six killed in Idlib were one schoolchild and three teachers," said Rami Abdel Rahman, the head of the UK-based monitoring group.
Another three people, one of them a child, were killed in strikes on Binnish, northeast of Idlib city.
According to the Observatory, pro-regime forces retook control of 15 villages and towns in the southern part of the Idlib enclave.
With backing from Russia, Syrian government and allied forces have in recent weeks pressed a major offensive against the last bastion of opposition to the regime.
The territory still held by militants and Turkish-backed rebels has shrunk to an area roughly the size of Majorca, hosting more than three million people -- half of them already displaced by violence elsewhere.
The offensive has displaced close to a million people since December, amid bitter winter cold.
Several countries and the United Nations have called for an urgent ceasefire in Idlib, where the current humanitarian emergency has been described as the worst since the start of the Syrian conflict nine years ago.
Russia earlier this month blocked a UN bid to end the Damascus regime's assault on Idlib.
Moscow's Foreign Minister Sergei Lavrov said Tuesday that a truce at this stage would be tantamount to "capitulating before terrorists".
The fighters who have controlled the Idlib region in recent years are dominated by Hayat Tahrir al-Sham, a militant group led by ex-members of Al-Qaeda's former Syria franchise.
Many of the crowded territory's residents are civilians who were forced from their homes in earlier phases of a war that has displaced more than 11 million people since 2011.
According to the UN's Office for the Coordination of Humanitarian Affairs, some 170,000 people are sleeping rough in Idlib province, which saw snow and sub-zero temperatures earlier this month.