MOSCOW - Russia said on Tuesday there was no credible evidence of its air strikes causing civilian deaths in Syria, rejecting German Chancellor Angela Merkel's criticism of the bombing campaign.Merkel said on Monday that Russian bombing had forced tens of thousands of Syrian civilians to flee, suggesting that the attacks violated a UN Security Council resolution that Moscow itself signed in December.European Council President Donald Tusk added to the pressure, saying the Russian actions were helping the "murderous" government of Syrian President Bashar Assad.Responding to Merkel's statement, made during a trip to Turkey, Kremlin spokesman Dmitry Peskov told journalists: "Despite a huge number of such statements, no one up to now has presented a single (piece of) credible evidence as proof of these words."There was also no way of talking about improving ties with Turkey, whose fighter jets shot down a Russian bomber near the Turkish-Syrian border in November, he added."Our relations are now in their worst shape for the past few decades," he said. "Turkey committed aggressive and dastardly acts against Russia. Turkey has not adequately explained its actions and has not apologized properly."He called "wrong and absurd" accusations by Turkish President Tayyip Erdogan that Russia was engaged in an invasion of Syria, trying to set up a "boutique state" for Assad."It's well-known that aerospace forces of the Russian Federation are in Syria following an invitation from the legitimate Syrian leadership," he said. "Hence, there can be no talk of any de jure or de facto occupation of Syria."