Turkey has decided to close its air space to planes flying to and from northern Iraq as it stepped up efforts to fight the separatist Kurdish Workers' Party (PKK), local private NTV reported on Thursday.

The decision is part of economic sanctions targeting groups supporting Kurdish militants operating in northern Iraq, the channel said, and it was not immediately clear whether the ban would affect U.S. military planes operating between NATO member Turkey and Iraq.

On Wednesday, Turkey said that it had taken economic measures designed to weaken Kurdish rebels and groups that support it, a step that could affect the economy in the self-governing Kurdish administration in northern Iraq.

Turkish government spokesman and Deputy Prime Minister Cemil Cicek said Wednesday that Turkey will "fight against terrorism in all areas" as the country was still weighing a cross-border operation to fight the PKK in northern Iraq.

Turkey has now massed up to 100,000 troops along the mountainous border with Iraq in preparations for a cross-border operation to crush about 3,000-strong PKK rebels, which was approved by the parliament earlier this month.

The PKK, listed by the U.S. and Turkey as a terrorist group, took up arms against Turkey in 1984 with the aim of creating an ethnic homeland in the southeast. More than 30,000 people have been killed in the more than two decade conflict.