A dozen Turkish tanks have rolled across the Syrian border after heavy Turkish shelling of an area held by so-called Islamic State (IS).

Military sources told Turkish media 70 targets in the Jarablus area had been destroyed by artillery and rocket strikes, and 12 by air strikes.

Turkish special forces entered Syria earlier as part of the offensive.

President Recep Tayyip Erdogan said the operation was aimed against both IS and Kurdish fighters.

Turkey shelled Syrian Kurdish forces in the region this week, determined not to let them fill the vacuum if IS leaves, the BBC's Mark Lowen reports from Gaziantep, near the Syrian border.

The concern in Ankara is that the Kurds could create an autonomous area close to the border which might foster Kurdish separatism within Turkey itself, our correspondent says.

In another development, counter-terror police in Turkey's main city, Istanbul, launched dawn raids targeting IS suspects across the city.

US Vice-President Joe Biden arrived in Turkey on Wednesday in the highest-ranking visit by a Western official since the failed coup on 15 July.