Syrian President Bashar al-Assad said the success of a military campaign by Russia, Syria, and its allies was crucial to save the Middle East from destruction.
“The alliance between Russia, Syria, Iraq, and Iran must succeed or else the whole region will be destroyed," Assad warned in an interview with Iranian television broadcast on October 4.
During the interview with Iran's Khabar TV, Assad said that the U.S.-led coalition to fight IS will only lead to more instability in his country and the region.
Assad's comments are the first since Russia launched an aerial campaign against rebel positions in Syria on September 30.
In Istanbul, Turkish President Recep Tayyip Erdogan called Russia's bombing campaign a "grave mistake."
"The steps Russia is taking and the bombing campaign in Syria are quite unacceptable to Turkey," Erdogan said.
The strikes will "isolate Russia in the region," he predicted.
Russia says its warplanes have flown 20 sorties in Syria over the past 24 hours, striking 10 Islamic State (IS) targets.
The Defense Ministry said on October 4 that the strikes hit a terrorist training camp, including a suicide belt factory.
It said the Russian air force managed to disrupt the IS group's supply lines and caused "significant damage to the infrastructure used to prepare acts of terror" since its strikes began on September 30.
Russian jets also targeted the IS stronghold of Raqqa as well as the western towns of Maarat al-Numaan and Jisr al-Shughour where rival insurgents are more prominent.
The West and the Syrian opposition say Russia's air strikes are supporting its ally Assad, and are also hitting non-IS rebels. Moscow denies the accusations.
Syrian activists say dozens of civilians have been killed in the strikes.
British Prime Minister David Cameron urged Moscow to "change direction" in Syria and recognize that Assad must be replaced.
"Tragically, what has happened is that most of the Russian air strikes, as far as we have been able to see so far, have been in parts of Syria not controlled by ISIL but by other opponents of the regime," Cameron said on October 4.
"They are backing the butcher Assad, which is a terrible mistake for them and for the world. It is going to make the region more unstable, it will lead to further radicalisation and increase terrorism."
In an interview with Reuters on October 4, British Foreign Secretary Philip Hammond said that Russia is engaged in “classic asymmetric warfare” in Syria by using its military power to keep President Bashar al-Assad in power while saying that they are fighting IS militants.
"It looks like a classic bit of Russian asymmetric warfare -- you have a strong propaganda message that says you're doing one thing while in fact you are doing something completely different and when challenged you just flatly deny it," Hammond said.
Hammond also criticized Russian proposals to hold elections as a means to end the conflict and said that Britain needed “absolute clarity” that Assad wouldn’t be part of Syria’s future.
On October 3, Moscow pledged to intensify its air strikes, saying about 600 militants have already abandoned their positions and were trying to escape to Europe.
With reporting by Reuters, AFP, and AP