Russia’s military operation against rebels in Syria began with a Russian air strike against the base of the Islamic State group in the country’s Idlib province, according to officials with knowledge of the operation.
The military operation, which is still ongoing, came amid reports of Russian jets flying over rebel-held areas in Idlib, according the U.S. and Russian officials, who spoke on condition of anonymity to discuss ongoing military operations.
The air strike on the base was the latest in a series of Russian strikes that have targeted the Islamic Republic’s Syrian military in recent weeks.
It comes amid an escalating conflict that has killed more than 270,000 people since March 4, including more than 400,000 in Aleppo, Syria’s largest city.
U.N. officials estimate that more than 300,000 civilians are in need of humanitarian aid.
Russian Foreign Minister Sergey Lavrov told reporters on Monday that the operation was launched on Friday.
“The military base was attacked by Russian jets,” he said.
“It’s a violation of international law.
I can’t say anything about the Russian side, but it is clear that this is an action that violates the rules of war.”
Russian warplanes struck the base on Saturday, a U.K.-based Syrian opposition activist told Reuters, as Russian warplanes continue to bomb rebel-controlled areas in northern Syria.
The strike came as the Syrian government said on Monday it had recaptured the town of Maarat al-Numan from the Islamic States of Iraq and the Levant group (ISIS), as well as the town near the border with Iraq.
In a statement, the Syrian army said that it had “reconquered Maarat el-Numah and all surrounding villages and towns.”
The army added that its troops have taken back control of the area around Maarat and that the Islamic extremist group has fled the area.
The Islamic State, which controls large parts of Syria and Iraq, declared a caliphate over the territory it controlled in Iraq and Syria in 2014.
It was responsible for the mass murder of more than 200,000 Muslims, including women and children, and the enslavement of large numbers of other people in Iraq, as well.
The group has been fighting for control of areas across northern Syria and is believed to have lost much of its territory to the Syrian regime.
Russian warplane in Syria The United States has condemned the air strike, saying it was a “grave violation” of international laws and principles and called on Russia to “immediately cease this aggression.”
In addition to Syria, Russia has been conducting air strikes against rebel forces in Iraq since September 2016, targeting the group in Mosul, and in the area of Raqqa province in the north of the country.
In recent months, Moscow has also bombed Syrian military and government targets in the western province of Idlib, killing more than 80 people.
The Russian air campaign in Syria has been supported by the United States, Saudi Arabia and Turkey.
Secretary of State John Kerry said last month that the Russian air operations in Syria were “one of the great humanitarian crises” of our time.