Turkeys' president has announced a new push by Turkish forces and Syrian rebels aimed at capturing a town held by the Islamic State group.

Recep Tayyip Erdogan says the Syrian opposition forces, backed by Turkish troops and tanks, are determined to advance toward al-Bab to clear the region of terror threats.

The Turkish leader said on Monday that the offensive will last until the area "is no longer a threat" to Turkey.

Last month, Turkey for the first time sent tanks across the border into Syria to help rebels clear territory of IS militants and to contain the expansion of a Syrian Kurdish militia.

Erdogan's announcement comes as a fragile cease-fire, brokered by the United States and Russia and now in its seventh day, has mostly held despite numerous violations.