Two waves of air strikes on a jihadist-held town in northwestern Syria have killed at least 13 civilians over the past 24 hours, a monitoring group said on Saturday.

Four children were among the dead in the early morning strikes on the Idlib province town of Khan Sheikhun on Friday and Saturday, the Syrian Observatory for Human Rights said.

Observatory chief Rami Abdel Rahman said the strikes were probably carried out by the Syrian air force, which has been carrying out an intensifying bombing campaign against jihadist targets in Idlib province alongside aircraft from ally Russia.

Like most of the rest of Idlib province, Khan Sheikhun is controlled by Hayat Tahrir al-Sham, an alliance of jihadist factions dominated by Al-Qaeda's former Syria affiliate.

The town hit the headlines in April when it was the target of a sarin gas attack that killed at least 87 people, 30 of them children.

US President Donald Trump blamed the Syrian government for the attack and ordered cruise missile strikes on the airbase from which he said it had been launched.

Damascus blamed jihadists on the ground for the deaths and received strong support for that position from Moscow.

A safe zone was supposed to be established in Idlib and adjacent areas of Hama and Latakia provinces under a deal reached in May by rebel backer Turkey and government backers Iran and Russia.

But during the summer the jihadists, who are not party to the agreement, drove out Islamist former allies from Idlib and took nearly full control.

Moscow says it has since killed 12 jihadist commanders and destroyed the group's largest arms depot.

But there has also been a heavy civilian death toll, according to the Observatory, a Britain-based monitoring group.

Source: AFP