Islamic State has reinforced fighters who are battling Kurdish forces for control of a Syrian town at the border with Turkey in the last day, a redeployment triggered by US-led air strikes on the group elsewhere, a Kurdish military official said.

Ocalan Iso, deputy leader of the Kurdish forces defending the town of Kobani at the Turkish border, said more Islamic State fighters and tanks had arrived since the U.S.-led coalition began air strikes on the group on Tuesday.

"The number of their fighters has increased, the number of their tanks has increased since the bombardment of Raqqa," Iso told Reuters by telephone.

Islamic State-controlled territory in the city and province of Raqqa was hit in the air strikes on Tuesday. He said Islamic State forces had advanced to within 8 km (5 miles) from the southern periphery of Kobani, which is also known as Ayn al-Arab - closer than they had been at any stage.

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