BEIRUT (Reuters) - Syria’s government said the U.S.-led military coalition have carried out a deadly air strike on a Syrian army camp, but officials from the U.S-led alliance said the report was false.

Syria said four coalition jets killed three soldiers and wounded 13 in the eastern Deir al-Zor province on Sunday evening, calling it an act of aggression, the first time it has made such an accusation.

Any such strike by U.S.-led coalition planes, which have been focusing their fire on Islamic State militants, would further complicate an increasingly regional conflict now nearly five years old.

The Syrian Observatory for Human Rights monitoring group reported earlier that jets likely to be from the coalition hit part of the Saeqa military camp near the town of Ayyash in Deir al-Zor province, killing four Syrian army personnel.

But Brett McGurk, U.S. President Barack Obama’s envoy to the coalition, said on his Twitter account: “Reports of coalition involvement are false.”

Colonel Steve Warren, a Baghdad-based spokesman for the U.S-led coalition, said the alliance had conducted four strikes in the Deir al-Zor province on Sunday, all against oil well heads.

“Our strikes were approximately 55 kilometers (35 miles)south east of Ayyash. We did not strike any vehicles or personnel targets. We have no indication any Syrian soldiers were near our strikes,” he said.

A U.S. defense official, who declined to be named, dismissed the idea that the coalition would target the Syrian military.

“We are not at war with the Assad regime and have no reason to target the Syrian Army,” the official said. “We are aware that Russia conducted long-range bomber strikes into Syria yesterday.”

Another U.S. defense official said Deir al-Zor was among the locations Russia had targeted on Sunday. Russian officials were not immediately available for comment.

The U.S.-led coalition first launched air strikes against Islamic State in Syria in September 2014, after beginning aerial operations against the group in neighbouring Iraq the previous month.

Its strikes have regularly targeted Deir al-Zor province in eastern Syria, most of which is held by Islamic State, including oilfields that are a source of income for the group.

The province links Islamic State’s de facto capital in Raqqa with territory controlled by the group in Iraq.

“FLAGRANT AGGRESSION”

Britain joined the United States and its allies last week in the bombing campaign against Islamic State in Syria, before proposed international peace talks later this month. Syria’s fragmented opposition are set to meet in Riyadh this week to try to unite ahead of the talks.

The Syrian foreign ministry said jets fired nine missiles at the camp, state TV reported.

The ministry sent letters to U.N. Secretary General and to the head of the U.N. Security Council condemning the “flagrant aggression,” state news agency SANA said.

It urged the United Nations to take “immediate action and take the necessary measures to prevent a repeat” of the incident.

The foreign ministry said three armoured vehicles, four military cars and a weapons cache and ammunition had also been destroyed.

The strikes “confirm once again that the American coalition lacks the seriousness and trust (needed) to fight terrorism in an effective way,” it said.

The Syrian government has only a limited presence in Deir al-Zor province, which is mainly controlled by Islamic State.

Syria’s ally Russia is waging its own air campaign in support of President Bashar al-Assad, and has also been striking in Deir al-Zor.

Russia’s air raids have hit some Islamic State targets, but the United States and its allies say most of them have hit other foreign-backed rebel groups.

In Deir al-Zor city, another air strike overnight killed a woman and two of her children, the Observatory said.