BEIRUT — The United States acknowledged Saturday that its warplanes had carried out an airstrike in Syria that resulted in the death of Syrian government troops.

US military officials said the pilots in the attack, in the eastern province of Deir el-Zour, believed they were targeting the Islamic State.

Russia’s Defense Ministry said the US attack had killed 62 Syrian troops, wounded 100 more, and opened the way for an Islamic State offensive.

A statement by US Central Command said the planes stopped the attack after a warning from Russia that the strikes could be hitting Syrian troops.

A senior Obama administration official, speaking on the condition of anonymity because the strike was being investigated, said the United States had relayed its regrets to the Syrian government through the Russians for the “unintentional loss of life of Syrian forces” fighting the Islamic State.


The episode comes at a time of escalating tensions in Syria. A partial cease-fire that started Monday continues to steadily unravel after it was declared with much fanfare by the United States and Russia.

Russia, the Syrian government’s main ally, said it would call an emergency UN Security Council meeting to discuss the strikes.

The Syrian government insisted that the strike was not a mistake. Instead, the government said it was “a very serious and flagrant aggression” that aided the Islamic State and proved its long-held assertion that the United States supports the jihadi group as part of an effort to oust President Bashar Assad.

“These attacks confirmed that the US clearly supports the terrorism of Daesh,” SAMA television, a state-run news outlet, said, using an Arabic acronym for the Islamic State, also known as ISIS.

The channel quoted a statement issued by the Syrian military’s general command, which said the attack exposed “false claims of fighting terrorism” by the United States.


Central Command denied it would carry out such an airstrike on purpose.

“Coalition forces would not intentionally strike a known Syrian military unit,” the statement said, offering at an unexpected moment one of the clearest statements yet of how far the United States has moved from three years ago.

In 2013, President Obama threatened to strike Assad’s forces in retaliation for chemical attacks on rebel-held suburbs that killed more than 1,000 people. He instead struck a deal with Russia to dismantle Assad’s chemical weapons program.

“Coalition forces believed they were striking a Daesh fighting position that they had been tracking for a significant amount of time before the strike,” the Central Command statement said.

“The coalition airstrike was halted immediately when coalition officials were informed by Russian officials that it was possible the personnel and vehicles targeted were part of the Syrian military,” it said.

Coalition jets last week hit oil pipelines, fuel trucks and other parts of the Islamic State’s oil infrastructure in the vicinity of Deir el-Zour, according to daily statements from Central Command. Three strikes destroyed four tanker trucks and the head of an oil well Tuesday, and strikes Thursday destroyed eight fuel trucks and seven wellheads, the statements said.

The Syrian army command said US warplanes had bombed an army base on al-Tharda mountain at 5 p.m., allowing “a wide terrorist offensive” by the Islamic State that allowed it to seize the base.

The accusation came as tensions have increased on numerous fronts in Syria’s complex, many-sided conflict. Russia backs the Syrian government and Assad, and the United States has called for him to step down. The powers have blamed each other as the cease-fire has eroded.


Residents of Deir el-Zour contacted on the Internet said there had been clashes Saturday between the Islamic State and government forces.

The strike began in the early evening, when planes began attacking a group of vehicles that US surveillance aircraft had been watching for several days, said a Central Command official who requested anonymity because the matter was being investigated.

Military intelligence had identified the cluster of vehicles, which the official said included at least one tank, as belonging to the Islamic State, the official said.

The attack went on for about 20 minutes, with the planes destroying the vehicles and gunning down dozens of people in the open desert, the official said. Shortly after this, an urgent call came into the US military command center in Qatar, which coordinates the aerial campaign in Syria and Iraq.

The call was from a Russian official who said the US planes were bombing Syrian government troops and should immediately call off the strike. The Central Command official said the attack was halted within minutes but not until dozens had been killed.

The Syrian Observatory for Human Rights, a monitoring group based in Britain with a network of contacts across Syria, quoted a government military source as saying that coalition warplanes had hit government positions and killed at least 30 soldiers.


Russian planes would have most likely been providing air support to government forces in the province during the fighting there. Russian warplanes were targeting the area of those clashes, according to the monitoring group.