President Tayyip Erdogan said on Tuesday Turkey will expand its cross-border operations against Kurdish militants after 13 captured Turks were killed in northern Iraq.

Turkey said on Sunday militants from the outlawed Kurdistan Workers Party (PKK) killed the captives, including police and military personnel, as it was carrying out a military operation against the group.

Erdogan also repeated Ankara’s complaint that it had not received enough international solidarity.

-Whether you speak up or not, we know our duty. We will not give the terrorists a chance- Erdogan told supporters from his AK Party in the Black Sea province of Trabzon.

-We will expand our operations into areas where threats are still dense- he added. -We will stay in the areas we secure as long as necessary to prevent similar attacks again.-

The PKK, designated a terrorist group by Turkey, the United States and European Union, has waged a decades-old insurgency in Turkey’s mainly Kurdish southeast. More than 40,000 people have been killed in the conflict.

In the past two years, Turkey has launched several cross-border operations to fight the PKK in northern Iraq, where the group has its stronghold in the Qandil mountains.

On Monday, the United States told Ankara that it blamed the PKK for killing the 13 Turks, after Turkey called an earlier U.S. statement on the killings “a joke” and summoned the U.S. ambassador.

Turkish Defence Minister Hulusi Akar, briefing parliament on the operation after opposition parties criticised the government for failing to rescue the Turks, said the offensive was launched without ground support due to the harsh conditions in the mountainous region.