22 February 2015
Last updated at 02:34
Kobane, just across the Turkish border, was retaken by Syrian Kurdish fighters in January
Turkish troops have reportedly crossed into Syria to relieve the garrison at the mausoleum of Suleyman Shah – a tiny enclave of Turkey where the forefather of the Ottoman empire is buried.
Sources say a large convoy, including tanks, passed through Kobane, the city which Syrian Kurdish fighters retook last month from Islamic State.
The sources say the Turkish operation was co-ordinated with the Kurds.
The operation is not believed to be a combat mission against the militants.
The border city of Kobane lies about 35km (20 miles) from the tomb of Suleyman Shah on the Euphrates River.
Suleyman Shah, the grandfather of Osman I, who founded of the Ottoman empire, is believed to have drowned in the river.
The tomb is permanently guarded by a contingent of about 40 soldiers, who rotate periodically. The site is part of Turkish territory, according to a treaty signed in 1921.
The Turkish convoy is believed to be larger and more heavily armed than usual because of recent heavy fighting between the Kurdish militia and Syrian rebel groups against IS militants.
Since driving IS out of Kobane in January, the Kurdish Popular Protection Units (YPG) and rebels have taken a number of surrounding villages.
They are now said to be only 25km from Tal Abyad – the strategically important border town east of Kobane that is used by IS militants to cross into Turkey.
Islamic State has seized larges swathes in Syria and Iraq, proclaiming a caliphate.