Turkey's military killed 18 Islamic State militants in northern Syria over the last 24 hours, the army said on Saturday, intensifying strikes against the militant group.

Four buildings and one vehicle used by the Islamic State fighters were destroyed in the strikes, an army statement said.

Separately, five Turkey-backed rebels and five Islamic State militants were killed in clashes on the ground, the army said in its statement. In addition, it said coalition forces conducted six air strikes which killed another 10 Islamic State militants.

Turkey is backing a group of Syrian Arabs and Turkmen in northern Syria in its Euphrates Shield operation, which has swept Islamic State from its southern border.

The hardline Sunni group claimed responsibility for a car bomb attack in the Turkish southeastern city of Diyarbakir that killed 11 last week.

However, an offshoot of the Kurdish militant Kurdish group PKK claimed the same attack. Kurdish militants, Islamic State radicals and far leftists have all staged attacks on civilians in Turkey in recent years.