More than 110 people were killed in an attack on a military academy in Syria on Thursday, with authorities vowing a strong response, sparking fears of an escalation, AFP reported.

The attack, which took place during an officer promotion ceremony in Homs (central Syria), was blamed on “terrorist organizations” by the Syrian army, which vowed a “firm response”. According to the army, the attack was carried out using “drones loaded with explosives”.

According to a new report by the Syrian Observatory for Human Rights (OSHR), a British organization with an extensive network of sources in Syria, the attack killed “112 people, including 21 civilians” and injured at least 120 others.

Syrian Health Minister Hassan al-Ghobash put the “preliminary” death toll at 80, “including six women and six children,” and about 240 wounded.

There was no immediate claim of responsibility for the attack, but the jihadist group, which controls parts of Syria, sometimes uses armed drones.

Government forces responded with bombings that residents said targeted the Idleb region, the last rebel stronghold in the country’s northwest. OSDH named eight dead and 30 wounded.

UN Secretary-General Antonio Guterres is “deeply concerned” by the attack in Homs, his spokesman Stephane Dujarric said. For his part, UN special envoy for Syria Geir Pedersen called for an “immediate de-escalation” of violence in Syria on Thursday.

The conflict in Syria, which began in 2011, has claimed more than half a million lives and divided the country. The United States, Russia, a regime ally, and Turkey have sent troops into Syria.

Meanwhile, Turkey’s defense ministry said in a statement released late Thursday that its forces had carried out airstrikes in northern Syria, destroying 30 targets, including “shelters, warehouses and storage sites.” Earlier on Thursday, Turkish media reported new strikes on Kurdish forces in Syria, saying an operation by MIT intelligence units “destroyed PKK/YPG weapons and ammunition caches.”

The Kurds have established an autonomous administration in northeastern Syria that is regularly targeted by the Turkish military. On Thursday, Turkish drones targeted oil facilities, two power plants, a dam and a factory during the day in Hassakeh province, which is controlled by the Syrian Democratic Forces (SDF), a Kurdish-dominated coalition. Kurdish forces announced that Turkey had carried out 21 strikes, killing 11 people, including five civilians and six security forces.

Turkey says it is taking action in response to Sunday’s suicide attack on the Interior Ministry in Ankara, which left two police officers injured.