Smoke billows during a reported air strike by pro-regime forces on the town of Hish in Syria's Idlib province on Aug. 19. (Omar Haj Kadour/AFP/Getty Images)

A Turkish military convoy was targeted by an airstrike in Syria on Monday, killing three civilians, Turkey’s Defense Ministry said in a statement. 

Syria’s government said the convoy contained weapons bound for insurgents, without saying whether it was behind the strike, which took place in Idlib province.   

The attack threatened to set off a new round of violence between the governments of Syria and Turkey and imperiled the fragile military cooperation between Moscow and Ankara in northern Syria, including agreements aimed at decreasing violence there.

While Turkey has been able to maintain observation posts in Idlib, its cooperation with Russia has not prevented the government of President Bashar ­al-Assad, Russia’s ally, from pursuing an all-out offensive to recapture the province from Syrian rebel groups. 

Turkey did not say who conducted the airstrike but at least partially blamed Russia. 

The Russian government had been supplied with “advance information” about the convoy’s route, the ministry said. The attack “contradicts the existing agreements, cooperation and dialogue with the Russian Federation,” it added, calling for “all necessary measures to be taken to prevent recurrence of such incidents.” 

Turkey maintained its right to respond in self-defense, the statement said. The convoy had set out for a Turkish observation post at 5:30 a.m. Monday and was attacked from the air shortly before 9 a.m. In addition to the three fatalities, 12 civilians were wounded. 

Syria’s government said in a statement of its own that the convoy had been loaded with “ammunition, weapons and material” intended for a Syrian jihadist group in Khan Sheikhoun, a target of the government offensive and one of the last major rebel redoubts. It called the convoy “a stark violation of the sovereignty and the territorial integrity of the Syrian Arab Republic.” 

Syria’s Russian-backed offensive in Idlib has killed hundreds of civilians since April and displaced hundreds of thousands of people, setting off fears of another refu­gee exodus from Syria, according to United Nations officials. Turkish President Recep Tayyip Erdogan, a longtime supporter of the Syrian opposition, has seemed powerless to blunt the offensive, despite his increasingly strong partnership with Russian President Vladi­mir ­Putin.    

Those ties grew even warmer in recent weeks, after Turkey took delivery of an advanced ­Russian air defense system, over the Trump administration’s ­objections.

But in Idlib, a series of cease-fires have collapsed, including a deal struck in early August. Syria’s government has accused the rebels of failing to abide by the terms of a deal between Turkey and Russia aimed at de-escalating the violence in the province. In recent days, a flurry of airstrikes have killed dozens of civilians across Idlib, according to activists.    

Turkey has previously retaliated after accusing Syria of carrying out deadly attacks against Turkish military personnel in Idlib. In June, Turkey fired heavy weapons into Syrian government-held territory after a Turkish soldier was killed in what Ankara said was a Syrian army attack.

Liz Sly in Beirut contributed to this report.