The government of Turkey is expressing “deep concern” regarding Russia’s prodigious military buildup in Syria, allegedly intended to keep Syrian dictator Bashar al-Assad in power against the jihadists of the Islamic State (ISIS/ISIL/IS).

Prime Minister Ahmet Davutoğlu said in an interview Monday that he believed Russia was dangerously exacerbating tensions in the region by expanding its presence. “[Russia] have taken [it] into the field. This is very dangerous. Therefore, we watch with deep concern,” he said. Davutoğlu expressed hope that his country would intervene and keep diplomacy on the forefront with Russia despite the nation’s strident support of Assad, while Turkey continues to demand that he be removed from power. He insisted once again that Assad is the “main [one] responsible and is [to] blame for the dangerous escalation which caused the problem to deepen.”

“İnşallah [God willing] Russia will not insist on ways and methods that will increase the tension,” he said, noting that he expected President Recep Tayyip Erdogan to discuss the matter with Russian head of state Vladimir Putin during his visit to Moscow Wednesday.

Erdogan is in Moscow at Putin’s request, along with a number of other Muslim leaders, to celebrate the opening of Russia’s biggest mosque in the capital. Putin used his speech celebrating the mosque to condemn the Islamic State, which has been extremely successful in recruiting Russian jihadists. “Muslim opinion leaders always contribute to the development of peace and common sense against extremism in Russia,” he said of his guests, including Erdogan, but the Islamic State’s “ideology is based on lies and blatant perversion of Islam.”

Erdogan also spoke at the event, addressing the migrant crisis throughout Europe specifically, as many are refugees of the Syrian civil war. “The solution to the refugee crisis cannot be achieved by closing the borders or leaving those people to die in the sea– It can only be achieved by transforming their countries into habitable places where the refugees can live,” he said. Turkey has taken in nearly two million Syrian nationals since the start of the civil war in 2011, and Erdogan has been vocal in opposing any support for Assad.

Russia, meanwhile, remains Assad’s strongest ally. Putin began flooding the nation with troops earlier this month, threatening the United States to cooperate or face “unintended consequences.” When news first broke of Russian reinforcements, the government claimed it was only sending in humanitarian aid, and when it became clear that Russian troops and weapons were entering Syria, Russian officials claimed they had “never concealed” the fact that they were arming Assad’s troops. This week, news surfaced that Russia has also begun flying drones in Syrian battlefields.