Family members of some of the victims of a deadly drone attack on a crowded military graduation ceremony that killed scores gathered outside a military hospital in the central city of Homs on Friday to collect the bodies of their loved ones, who died in one of Syria’s deadliest single attacks in years.

Thursday’s strike on the Homs Military Academy killed 89 people, including 31 women and five children, and wounded as many as 277, according to the health ministry. The death toll could rise as some of the wounded are in critical condition. Syria announced a three-day state of mourning starting Friday.

The attack is likely to lead to a renewed wave of violence in the country’s opposition-held northwest, where front lines have been relatively calm since Russia and Turkey, who support rival sides in the country’s conflict, reached a cease-fire in March 2020, ending a three-month Russian-backed government offensive against insurgents.

No group immediately claimed responsibility for Thursday’s attack as Syria endures its 13th year of conflict that has killed half a million people. In the aftermath, Syrian government forces intensified their shelling and airstrikes on rebel-held regions and insurgents fired back toward areas held by President Bashar Assad’s forces.

The attack was an indication that the war is far from over and a sign of weakness within the Syrian military, which failed to prevent it despite the fact that the army has regained control of most of Syria in recent years with the backing of Russia and Iran.

The last such large-scale killing against government forces came in 2014, when the Islamic State group killed more than 160 Syrian government troops at a military base in the northern province of Raqqa. In a video released at the time, dozens of terrified young conscripts were made to run while stripped down to their underwear before being killed.

Around noon on Friday, the Syrian military fired machine guns toward another drone that flew over Homs, two pro-government media outlets, Al-Watan and Sham FM, reported. It was not immediately clear if the drone was shot down.

The city of Homs is about 100 kilometers (60 miles) south of rebel-held areas, indicating that insurgents might have acquired weaponized long-range drones.

Fearing retaliation from the government, religious authorities in areas held by the opposition in northern Syria said Friday prayers will not be held in mosques and called on people to pray at home instead “out of concern for the safety of Muslims.”

Syria’s military said in a statement Thursday that drones laden with explosives targeted the ceremony packed with young officers and their families as it was wrapping up. Without naming any particular group, the military accused insurgents “backed by known international forces” for the attack and said “it will respond with full force and decisiveness to these terrorist organizations, wherever they exist.”

Overnight, Syrian troops pounded the last major rebel-held region in parts of Idlib and Aleppo provinces, killing at least three people and wounding more than 15 in the town of Daret Azeh, according to the opposition’s Syrian Civil Defense, also known as White Helmets. The group reported that a child was killed in another strike in a village in the region.

The Britain-based Syrian Observatory for Human Rights, an opposition war monitor, reported that Russian warplanes carried out several airstrikes on the town of Jisr al-Shughour and nearby villages on Friday. The area is a stronghold of the Turkistan Islamic Party, a Uyghur militant group, many of whose fighters are Chinese Muslims.

In Homs, hundreds of people, many of them dressed in black and weeping, gathered outside the Abdul-Qader Shaqfa Military Hospital where the bodies of 30 victims in coffins draped with Syrian flags were put in ambulances to be taken to their hometowns for burial.

Army Lt. Ibrahim Shaaban came to collect the body of his fiancee, Raneem Quba, 23, who was killed along with her father, Mohammed, and younger sister, Rima, while attending the graduation of her brother, Lt. Hussein Quba.

“I feel that my back was broken,” Shaaban said, holding back his tears while standing by her coffin. “She was not only a fiancee, but a mother, a sister and a friend.”

Legislator Bassam Mohammed said targeting a place where civilians are present “is a terrorist criminal act,” and that the attackers intended to inflict large numbers of casualties.

Syrian Defense Minister Gen. Ali Abbas was present Friday outside the hospital, where he comforted the families of victims. An opposition war monitor reported Thursday that Abbas had left the graduation ceremony shortly before the attack.

“We will go after them and after those who support them,” Abbas said of the insurgents. “We will avenge the blood of martyrs and clean Syria’s soil from terrorists and criminals.”

One of the survivors, Lt. Jaafar Mohammed, 23, said he was taking photos with relatives by the platform when something suddenly exploded in front of them.

“I was thrown to the ground,” said Mohammed, who suffered an arm injury. He said his brother was killed and his father and younger brother were also injured.

Syria’s crisis started with peaceful protests against Assad’s government in March 2011 but quickly morphed into a full-blown civil war after the government’s brutal crackdown on the protesters. The tide turned in Assad’s favor against rebel groups in 2015, when Russia provided key military backing to Syria, as well as Iran and the Lebanese militant group Hezbollah.