Turkish Prime Minister Recep Tayyip Erdogan on Sunday expressed concern over the deteriorating situation in northern Iraq after Islamic State in Iraq and the Levant (ISIL) militants began to attack Mosul's Telafer district where thousands of Turkmen are believed to live, local Daily News said.

"The developments in Telafer are something that cannot be underestimated. As is known, Telafer is an area mainly inhabited by Turkmen. Almost half of the Turkmen there are Sunni, but the other half are Shia," Erdogan said during a rally in Turkey's Trabzon on Sunday.

The prime minister said that Turkey is highly vigilant against the development of the situation and prepared for any step to cope with it.

His statement came just few hours after the Turkish Foreign Ministry warned that the crisis in Iraq had gained a dimension of "sectarian clashes" and urged its citizens to leave the country as soon as possible.

Turkish media said that at least five Turkish citizens had been killed after ISIL launched an attack in the Telafer district on Sunday.

ISIL militants captivated 31 Turkish truck drivers on Tuesday after they captured Mosul. On Wednesday they took control of the Turkish consulate, kidnapping 49 staff and their family members, including the consul-general.