Turkish shelling and air strikes killed at least 40 Syrians on Sunday, a monitor said, in the first significant civilian casualties in Turkey’s intensifying campaign in northern Syria.

Turkey’s state-run Anadolu news agency said the army had killed 25 Kurdish “terrorists” in air strikes as part of its unprecedented operation inside Syria.

The bombardments came after Ankara suffered its first military fatality since it launched the two-pronged offensive against the Islamic State group and Syrian Kurdish militia inside Syria on Wednesday.

At least 20 civilians were killed and 50 wounded in Turkish artillery fire and air strikes on the village of Jeb el-Kussa early on Sunday, the Syrian Observatory for Human Rights monitoring group said.

Another 20 were killed and 25 wounded, many seriously, in Turkish air strikes near the town of Al-Amarneh, it said.

The monitor also said at least four Kurdish fighters had been killed and 15 injured in Turkish bombardment of the two areas.

A spokesman for the local Kurdish administration said 75 people had been killed in both villages.

The Britain-based Observatory said the bombardment targeted an area south of the former IS border stronghold of Jarabulus, which Turkish-led forces captured on the first day of the incursion.