Turkish forces have stopped thousands of Kurds fleeing Islamic State fighters in northern Syria from crossing the border.

About 3,000 people have fled their homes after the militants used tanks to seize control of 21 Kurdish villages in the Kobani area near the Turkish border.

For more than a year, Islamic State and Kurdish militias have clashed in the area, but IS appeared to have gained the upper hand since Wednesday.

A spokesman for Syria's powerful Kurdish Democratic Union Party called on Kurds around the world to come to Syria to defend Kobani.