Separately, in the war-torn country's Kurdish-held northeast, Turkish strikes on military and infrastructure targets killed at least nine people, according to Kurdish forces, after Ankara had threatened raids in retaliation for a bomb attack.
In the central Syrian city of Homs, "armed terrorist organisations" targeted "the graduation ceremony for officers of the military academy", an army statement carried by official news agency SANA said, reporting casualties.
The Syrian Observatory for Human Rights, a Britain-based group with a vast network of sources in the war-torn country, reported "more than 100 dead, around half of them military graduates, and including 14 civilians", with more than 125 others wounded.
There was no immediate claim of responsibility.
The attack was carried out with "explosive-laden drones", according to the military statement.
The general command of the army and the armed forces decried the "cowardly... unprecedented" attack and said it would "respond with full force", the statement added.
The Syrian government retook full control of Homs, Syria's third-largest city, in 2017.
Later on Thursday in the rebel-held Idlib region, residents reported wide and heavy regime bombardment.
The Idlib rebel bastion in Syria's northwest is controlled by Hayat Tahrir al-Sham (HTS). The jihadist group, led by the former local Al-Qaeda branch, has used drones to attack government-held areas in the past.
Meanwhile, the Turkish strikes on Hasakeh province in Kurdish-held northeast Syria "killed six members of the internal security" agency, a statement from the Kurdish force's media centre said.
A worker at a site in the province was also killed, according to Farhad Shami, spokesman for the Kurdish-led Syrian Democratic Forces (SDF), the Kurds' de facto army.
The Kurdish authorities' statement also said "two civilians" were killed in a strike on a motorcycle.
Turkey regularly strikes targets in Syrian Kurds' semi-autonomous region.
On Wednesday, Ankara warned of more intense cross-border air raids, after concluding that militants who staged a weekend attack in the Turkish capital came from Syria.
The US-backed SDF led the battle that dislodged Islamic State (IS) group fighters from their last scraps of Syrian territory in 2019.
Turkey views the Kurdish People's Protection Units (YPG) that dominate the SDF as an offshoot of the Kurdistan Workers' Party (PKK), which is listed as a terror group by Turkey and its Western allies.
Since Sunday's Ankara attack, which wounded two Turkish security officers and was claimed by the PKK, Ankara has launched strikes on the Kurdish group's positions in northern Iraq.
AFP correspondents in Syria's northeast saw black smoke rising from oil sites near Qahtaniyeh, close to the Turkish border.
Two power stations in the area were also hit, the correspondents said.
The SDF's Shami said the strikes had targeted military and civilian sites.
"There has been a clear escalation since the Turkish threats," he said, reporting intensive overflights of Kurdish-held areas in northeast Syria.
Turkish Foreign Minister Hakan Fidan had warned of reprisals against Kurdish fighters in northeastern Syria in the aftermath of Sunday's attack outside the interior ministry in Ankara.
He had alleged the perpetrators "came from Syria and were trained there".
"From now on, all infrastructure, large facilities and energy facilities belonging to (armed Kurdish groups) in Iraq and Syria are legitimate targets for our security forces," Fidan had said in televised comments.
In the market of the city of Qamishli in Hasakeh province, vendors were anxiously following the escalation on their mobile phones and televisions.
"The situation is worsening every day. Turkey doesn't let us breathe," said Hassan al-Ahmad, a 35-year-old fabric merchant.
SDF commander Mazloum Abdi denied Wednesday that the Ankara assailants had "passed through our region".
"Turkey is looking for pretexts to legitimise its ongoing attacks on our region and to launch a new military aggression," he said.
The Kurdish administration on Thursday called on "the international community, the international coalition" and Russia to "take a stand capable of dissuading" Turkey from its attacks.
State Department spokesperson Vedant Patel said the United States "remains concerned about the military escalation in northern Syria".
The United States, Russia and Turkey all have troops in areas of the war-torn country.
Between 2016 and 2019, Turkey carried out three major operations in northern Syria against Kurdish forces.
The conflict in Syria has killed more than half a million people since it began in 2011 with a brutal crackdown on anti-government protests, spiralling into a complex battlefield involving foreign armies, militias and jihadists.