Syria Democratic Forces (SDF) fighters walk on the rubble of damaged shops and buildings in the city of Manbij, in Aleppo Governorate, Syria, Aug. 10, 2016. Photo: Reuters / Rodi Said / File.

Four Turkish soldiers were killed and two others wounded in two separate attacks by Kurdish militants on Saturday, the Turkish defense ministry said, adding that the army had retaliated in both cases.

One Turkish soldier was killed and another was wounded in an attack by the Syrian Kurdish YPG militia in the mainly Kurdish-controlled northern Syrian region of Tel Rifaat, the defense ministry said in a statement.

The attack took place in a region where Turkey carried out a cross-border operation dubbed Euphrates Shield in 2016, aimed at driving Islamic State militants and the YPG from its border with Syria, the ministry said.

Turkish Defense Minister Hulusi Akar was later quoted by the state-run Anadolu news agency as saying the military had killed 23 militants in retaliation for the attacks from Syria.

A Turkish security official told Reuters that the army was carrying out small operations to eliminate threats from the Tel Rifaat region, but that it could launch “a bigger operation” if necessary.

Separately, three Turkish soldiers were killed and another wounded in the southeastern Turkish province of Hakkari, which borders northern Iraq, after Kurdish militants shelled the region, the defense ministry said in a separate statement.

It said the military had returned fire and launched a cross-border operation in the region backed by fighter jets to destroy militant targets.

Akar said the military had killed five other militants in the cross-border operation into northern Iraq, and a total of 28 militants in response to the two attacks.

“We neutralized the 28 terrorists who carried out the attacks. Our operations both inside and outside our country continue with great determination,” Akar said, according to Anadolu.

Turkey’s military has regularly carried out air strikes against Kurdish militants in northern Iraq. It also shelled YPG positions in the Tel Rifaat region earlier this year, saying this was in response to YPG fire.

Tel Rifaat is controlled by Kurdish-led forces and is located some 20 km east of Afrin, which has been under the control of Turkey and its Free Syrian Army (FSA) allies since an operation last year to drive out the YPG.

Turkey, which has long been one of the main backers of rebel groups fighting against Syria’s President Bashar al-Assad, has conducted patrols with Russia, one of Assad’s main allies, in northern areas under agreements reached last year.

In March, the defense ministry said Turkish and Russian forces had carried out the first “independent and coordinated” patrols in Tel Rifaat.