At least 100 people were killed on Thursday in an attack on a military academy in Syria with weaponised drones bombing the site minutes after Syria's defence minister left a graduation ceremony there.
Civilians and military personnel were killed in the attack on the academy in the central province of Homs, Syria's defence ministry said in a statement, adding "terrorist" groups had used drones to carry it out.
The statement did not specify an organisation and no group immediately claimed responsibility for the attack.
Syria's defence and foreign ministries vowed in written statements to respond "with full force" to the attack. Syrian government forces have carried out heavy bombings on the opposition-held zone of Idlib throughout the day.
"After the ceremony, people went down to the courtyard and the explosives hit. We don't know where it came from, and corpses littered the ground," said a Syrian man who had helped set up decorations at the academy for the occasion.
Syria's conflict began with protests against President Bashar al-Assad in 2011 but spiralled into an all-out war that has left hundreds of thousands dead and millions displaced.
Assad regained most of the country, but a swathe in the north bordering Turkey is still held by armed opposition groups.
US President Donald Trump and Iran threatened to escalate their war by attacking energy and desalination facilities in the Gulf, a potential widening of hostilities that could deepen a regional crisis and add to concerns in global markets.
An Israeli airstrike on a police vehicle on Sunday killed three people in the middle of the Nuseirat camp in the central Gaza Strip, health officials said, hours after another person was killed in a strike on northern Gaza.
The Strait of Hormuz remains open to all shipping except vessels linked to "Iran's enemies", Iran's representative to the UN maritime agency was quoted as saying in Iranian media reports published on Sunday.
The Gulf Cooperation Council (GCC) has renewed its condemnation of continued Iranian attacks on member states, including the targeting of infrastructure and oil facilities, in flagrant violation of international law and a direct threat to regional security, stability and the safety of global energy supplies.