Turkey has sent more tanks into northern Syria, in an operation against the Islamic State (IS) group, Turkish media reports say. The tanks crossed the border near the Turkish town of Kilis and journalists later heard firing and saw plumes of smoke rising on Syrian territory. Civilians were seen fleeing as the Turkish military advanced. The tanks were backed by artillery, which fired on IS positions in the area, Turkish media said. The reports said about 20 tanks, five armoured personnel carriers and other armoured vehicles were involved in the assault.