Turkey's foreign ministry has summoned Russian and Iranian ambassadors for what Ankara says Syrian government forces' escalation of violence in the city of Idlib, diplomatic sources told Al Jazeera.

Russia's ambassador to Ankara, Alexei Yerkhov and Iranian ambassador Mohammad Ebrahim Taherian Fard were called in to express Turkey's "discomfort" about the attacks in Idlib, officials, who asked to remain anonymous, said on Tuesday.

Turkey had previously voiced its discontent to Russian and Iranian officials via military and diplomatic channels about the government forces' violations of de-escalation zones, according to the sources.

{articleGUID}

Idlib is located within one of the so-called de-escalation zones set up in Syria last September in an effort to scale back the conflict.

However, as the fighting continues, tens of thousands of civilians are fleeing the area, which is home to about two million people.

Believed to be the largest remaining rebel-held area in Syria, hospitals, markets and bakeries across Idlib province have been hit by government air raids.

Guarantor states

Turkish Foreign Minister Mevlut Cavusoglu on Wednesday called on the governments of Iran and Russia to meet their obligations as guarantor states in Syria.

"Iran and Russia should fulfil the responsibilities [as guarantor states] in Syria," Cavusoglu said in remarks published by state media.

He said that the Syrian government forces were targeting the moderate opposition groups "on the pretext of fighting al-Nusra terrorist group".

"If you are the guarantors - yes, you are - you should stop the regime. It's not just a simple air attack. The regime is moving in Idlib. The intent here is different."

Cavusoglu warned that such a move would undermine the peace process in Syria.