Turkey-backed armed groups have fired back against government positions in Syria in retaliation for Russian airstrikes earlier in the week. On Tuesday, Syrian opposition groups fired hundreds of artillery rounds and missiles in northwestern Syrian.

The attack was in retaliation for an airstrike allegedly launched by Russia on one of the group's elite training camps Monday. The group said that the attack killed more than 50 of its fighters and dozens more injured. Unofficial reports claimed that the camp's leaders were among those killed.

The retaliatory attack has undermined the already fragile cease-fire between Russia and Turkey, which has already been strained by Ankara's increased involvement in the region. Russia has been backing Syrian President Bashar Assad's government, while Turkey has backed rebel groups under the National Front for Liberation banner.

The United Nations has called on the two nations to immediately "contain the situation" to avoid any further loss of lives on both sides. Sources with knowledge in the matter said Turkish Foreign Minister Mevlut Cavusoglu had talked with Russian officials over the phone to discuss the Monday attack along with the current situation in the Nagorno-Karabakh region. No details regarding the conversation were disclosed.

Turkey had openly blamed Russia over the airstrike in Idlib on Monday, which was the deadliest such attack since the two nations brokered a truce. The strike hit a training camp in northwestern Syria operated by the Turkish-backed Faylaq al-Sham militia.

Following the attack, the group promised on social media it would retaliate and that Russia would have to answer for its crimes. The group made good on its word and fired hundreds of projectiles at close to 30 government outposts in various locations in southern Idlib, Latakia and western Aleppo.

The Britain-based Syrian Observatory for Human Rights said that the attacks had resulted in the deaths of at least 12 Syrian soldiers and allied fighters. The National Federation for Liberations claimed that its soldiers had killed several Russian officers in southern Idlib. The report was not immediately verified and Russia has yet to issue a statement regarding the matter.