As part of the U.S.-led coalition against ISIS, Turkey allows coalition planes to fly raids on ISIS targets in neighboring Iraq and Syria from its territory.

And last year Turkey resumed hostilities with the PKK, Kurdish militant separatists, in earnest after a two-year cease fire broke down.

The PKK, or Kurdistan Worker’s Party, has been in an armed struggle with the Turkish government for decades and is considered a terror group by Turkey, the United States and the European Union.

In March, at least 37 were killed when a car bomb detonated near a bus stop in the Turkish capital, Ankara, in an attack claimed by a Kurdish militant group.

Six days later an ISIS suicide bomber detonated himself on one of Istanbul’s main streets, killing four.

A month earlier, 28 were killed in a blast targeting military vehicles in central Ankara. A Kurdish group claimed responsibility.

And in January, at least 10 German tourists died in a suicide bombing in Istanbul’s Sultanahmet Square that Turkish authorities linked to ISIS.

The violence has had an impact on Turkey’s tourism industry, a key sector of the national economy.