The US May Have Just Attacked the Assad Regime for the First Time

The Syrian government is accusing the United States and its allies of striking a military camp on Sunday in what would be the first US attack on soldiers loyal to Bashar al-Assad.

Three Syrian soldiers died when missiles struck an army camp in the Deir Ezzor province, the Syrian Foreign Ministry said on Monday, calling the attack an act of "flagrant aggression."

Syria claimed that the attack was carried out by four coalition warplanes, which fired nine missiles, destroying three armoured vehicles, four military vehicles, heavy machine-guns, and an arms and ammunition depot. It's the first time since the Syrian civil war began nearly four and a half years ago that Syria has accused the US of directly attacking its army. Though it's well known that the CIA actively trains many of the rebel group's seeking to overthrow the Assad regime.

The US has repeatedly insisted that the US and its allies are not responsible for the attack.

"We've seen those Syrian reports but we did not conduct any strikes in that part of Deir Ezzor yesterday. So we see no evidence," said Colonel Steve Warren, spokesman for the coalition. "We struck 55 km away from the area that the Syrians say was struck. That was the only area in Deir Ezzor we struck yesterday," he said, adding that "there were no human beings in the area that we struck yesterday, all we struck was a wellhead."

Related: A Little Bombing, a Lot of Surveillance: What Britain Brings to the Syria Air War

Most of Deir Ezzor province is controlled by the Islamic State (IS), and has been under heavy bombardment by the US and its allies for over a year. The province is a key region for IS — it's home to much of its oil wealth in Syria, and it links the group's capital in Raqqa with territory under its control in western Iraq.

Over the past few weeks, the US and its allies have intensified attacks in Deir Ezzor, targeting IS oil infrastructure.

Though IS holds sway over nearly all of the province, a small sliver — including the Deir Ezzor airport — is still under Syrian government control. The city of Dier Ezzor itself is divided between IS and the Syrian army.

On Monday, the Syrian government responded angrily to the alleged attack on its installation, and used the opportunity to criticize the US's commitment to fighting the Islamic State.

"The aggression on the military post hinders the efforts aiming to fight terrorism and reiterates that the US-led coalition lacks seriousness and credibility in the fight against terrorism," the Foreign Ministry statement said.

The Foreign Ministry also penned a letter to the UN secretary general and the Security Council demanding "urgent measures," in response to the attack.

The UK-based Syrian Observatory for Human Rights confirmed that the strikes against the Syrian army did take place, and reported four killed and 13 wounded, but could not confirm the source of the attack.

Related: 'I Know You Are But What Am I': Turkey, Russia, and the Islamic State's Oil

Meanwhile, an anonymous Pentagon official told the Washington Post on Monday that Russia was responsible for the attack. That official said that the US was "certain" that Russia carried out the strike, but offered no further evidence or explanation. An activist with the group Raqqa is Being Slaughtered Silently, based in Deir Ezzor, told VICE News that no one is sure who carried out the attack.

"But I think it was Russian airstrikes," he said.

The sky above Deir Ezzor has become crowded of late, with French, British, US, and Russian planes flying missions in the area. Since Russia began flying missions in Syria in late September, its strikes have largely targeted non-IS groups on the front lines in the Aleppo province. But in recent weeks, Russia has begun to target more IS positions in and around Deir Ezzor and Raqqa.

Since the Syrian army's positions in Deir Ezzor are just miles from the front lines with IS, it's conceivable that any of the powers operating in the skys could have mistakenly launched the attack.  As of Monday, Russia did not comment on the anonymous accusations from the US blaming it for the strikes.

Watch VICE News' documentary Jihadists vs. the Assad Regime: Syria's Rebel Advance: