Stopping attacks by the Syrian regime is the responsibility of Russia and Iran as guarantor states of peace, Turkey’s foreign minister said Sunday, hours after an Assad regime attack on a Turkish observation post in northwestern Syria.

Axar.az reports citing Turkish media that, Earlier Sunday, Assad regime forces attacked a Turkish observation post in Idlib, Syria -- with no casualties -- and was retaliated upon by heavy weapons, Turkey’s Defense Ministry said.

"Turkey won't tolerate Syrian regime harassment of its soldiers," Mevlut Cavusoglu told a ceremony inaugurating a Foreign Ministry office in Hatay, a southern Turkish province bordering Syria.

Cavusoglu stressed that Turkey "will teach them their place."

On Saturday, the Turkish military sent reinforcements to another observation post in Idlib near Zawiya, which was targeted by regime forces last week, leaving three Turkish soldiers wounded.

Although Turkey and Russia have agreed to stop acts of aggression and turn Idlib into a de-escalation zone, the Syrian regime has consistently violated the cease-fire, launching frequent attacks inside the de-escalation zone.

Syria has been locked in a vicious civil war since early 2011, when the Assad regime cracked down on pro-democracy protests.

Since then, hundreds of thousands of people have been killed and more than 10 million others displaced, according to UN officials.

S-400 defense system issue

On Turkey’s purchase of Russian S-400 missile defense systems, Cavusoglu reiterated that Turkey absolutely will not accept any U.S. impositions on the deal.

Tensions between the U.S. and Turkey have simmered over Ankara’s purchase of the S-400s.

Washington claims the purchase will jeopardize Turkey's role in the F-35 fighter jet program and has threatened sanctions.

Turkey has said there is no conflict between the S-400 and the F-35 and has called for a working group to clarify the issue.

Ankara is set to take delivery of the first S-400 as early as next month.

Stating last week that NATO can only protect 30% of Turkey’s airspace, Cavusoglu said of the S-400 deal: “This is surely a national cause.”