Turkey yesterday called on Russia and Iran, the two chief allies of President Bashar al-Assad's regime in Syria, to halt an air offensive on the rebel-held Idlib province near the Turkish border.

Ankara has been working closely with Russia and Iran to end the Syrian conflict over the last months but has stepped up pressure on Moscow and Tehran as the bombardments on Idlib intensified.

"Iran and Russia should fulfil their responsibility. If you are guarantors -- and you are -- they should stop the regime," Foreign Minister Mevlut Cavusoglu told the official Anadolu news agency.

"This is not a simple air offensive. The regime is advancing inside Idlib. They have a different intention."

Cavusoglu emphasised that in efforts to bring peace to Syria, Russia and Iran were the "guarantors" of the regime side and Turkey of the opposition.

Idlib province is almost entirely controlled by anti-government forces that are dominated by a jihadist outfit known as Hayat Tahrir al-Sham (HTS) consisting mostly of former fighters from the Al-Nusra Front, an Al Qaeda affiliate.

Ankara has already summoned the Russian and Iranian ambassadors, in the biggest public flare-up of tensions with Moscow and Tehran in months.

It conveyed "uneasiness" to the Russian ambassador Tuesday, calling the strikes a "violation of the borders of the Idlib de-escalation zone" established by Turkey, Iran and Russia, according sources at the foreign ministry.