The West’s Syrian Kurdish allies announced on Wednesday that they were halting all operations against Isil as they rushed their forces to face the long-awaited Turkish assault on northeast Syria.

Turkey unleashed a wave of airstrikes and artillery bombardment against the Syrian Democratic Forces (SDF) along the Turkish border but also struck deeper inside Syria, possibly indicating a wider offensive than initially expected.

At least two civilians were killed in the first hours of the attack, the SDF said, and the roads along the border were clogged with cars and trucks as thousands of terrified people fled for safety.

Recep Tayyip Erdoğan, the Turkish president, said the offensive would be known as Operation Peace Spring and was designed to push back the SDF, which Turkey considers a terrorist group.

“Our mission is to prevent the creation of a terror corridor across our southern border, and to bring peace to the area,” he said.