Rased News Network via Associated Press
FILE - This picture released on July 13, 2015 by the Rased News Network, a Facebook page affiliated with Islamic State militants, shows Islamic State militants fire weapons during a battle against Syrian government forces, in Deir el-Zour province, Syria. .

BEIRUT — Syria's government on Monday accused the U.S.-led coalition of launching airstrikes on an army camp that killed three soldiers and wounded 13, which if confirmed would mark the first time U.S.-led forces have struck troops loyal to President Bashar Assad.

The U.S. denied the claim, saying the alliance carried out four airstrikes against oil wells in the eastern province of Deir el-Zour — all of them miles away from where the incident was said to have taken place.

Iraq meanwhile demanded the withdrawal of additional Turkish forces sent in last week to expand an anti-IS training mission in the country's north, further highlighting the deep rifts among the various states battling IS, which have hindered efforts to roll back the extremist group.

The city of Der el-Zour, where the strikes are said to have been carried out on Sunday, is mainly held by the Islamic State group, but the Syrian government maintains a presence in some parts of it. A U.S.-led coalition has been striking at IS targets in Syria for the past year, and France and Britain recently began carrying out their own airstrikes. Russia is also carrying out airstrikes, in coordination with Damascus.

The Britain-based Syrian Observatory for Human Rights, which relies on a network of activists inside Syria, also reported the airstrikes and gave a similar death toll. The Observatory said the strikes were "believed" to have been carried out by the U.S.-led coalition.

The planes hit the camp known as "Sa'iqa,"the Observatory said, though it gave a slightly different account for its location, saying the camp is near the village of Ayyash in the western countryside of Deir el-Zour.

The U.S.-led Combined Joint Task Force, which coordinates coalition activities against IS, said in a statement that the alliance carried out four airstrikes solely against wells in Deir el-Zour province, all of them some 55 kilometers (34 miles) southeast of Ayyash.

"We did not strike any vehicles or personnel targets in this area. We have no indication any Syrian soldiers were even near our strikes," the statement said, adding that it takes allegations of potential collateral damage seriously and investigates them.

The Obama administration has repeatedly called on Assad to step down, but has refrained from targeting his forces, fearful of being dragged deeper into the country's increasingly complex civil war.

In a letter sent to the United Nations and published in Syrian state media on Monday, the government in Damascus said four aircraft belonging to the U.S.-led coalition targeted the army camp in the eastern city of Deir el-Zour on Sunday night. It said the attack destroyed armored and other vehicles as well as a weapons and ammunition depot.

"This hampers efforts to combat terrorism and proves once again that this coalition lacks seriousness and credibility to effectively fight terrorism," the Syrian letter said. The government refers to all those fighting to overthrow Assad as "terrorists."

On Sunday, airstrikes hit several IS positions in its de facto capital of Raqqa in northern Syria, killing and wounding at least 32 IS fighters according to several anti-IS activists. IS media accused the Russians of being behind those attacks and claimed civilians were killed.

Iraq's Foreign Minister Ibrahim al-Jaafari meanwhile warned that the deadline for the withdrawal of the additional Turkish forces expires Tuesday, after which Iraq will bring the matter before the U.N. Security Council.

Turkey says its troops have been stationed at a small base outside the IS-held city of Mosul since last year as part of a training mission coordinated with the Iraqi government. However, the arrival of additional Turkish forces on Friday sparked uproar in Baghdad.

Iraqi Prime Minister Haider al-Abadi has repeatedly called for the forces to be withdrawn, while a number of other senior Iraqi politicians have called the move a violation of Iraq's sovereignty.

Turkey said Sunday that additional deployments to Iraq would be halted until the Iraqi government's "sensitivities are overcome."

U.S. officials say the deployment is part of an agreement between Turkey and Iraq and does not involve the U.S. or the coalition. The officials say the mission is to train and advise Iraqi forces so they can eventually take back Mosul, the country's second-largest city.

Meanwhile, a new analysis released Monday by the conflict monitoring group IHS estimated the Islamic State group's overall monthly revenue in late 2015 to be around $80 million, most of it coming from the collection of taxes in areas under its control in Syria and Iraq.

The analysis of open source intelligence, including social media, conducted by the group said around 50 percent of revenues comes from taxation and confiscation, while around 43 percent comes from oil. Drug smuggling, the sale of electricity and donations make up the remainder.

"Unlike al-Qaida, the Islamic State has not been dependent on money from foreign donors, to avoid leaving it vulnerable to their influence," said Columb Strack, senior analyst at IHS, and lead analyst for the IHS Conflict Monitor.

The US-led coalition has focused primarily on disrupting the IS group's oil income, stepping up airstrikes in recent weeks on oil fields and facilities. IHS said the airstrikes have significantly degraded the group's refining capacity and ability to transport oil via tanker convoys. It did not elaborate.

Associated Press writer Adam Schreck in Dubai, United Arab Emirates, and Susannah George in Baghdad contributed to this report.