DAMASCUS, Syria – Syria’s 16-month bloodbath crossed an important symbolic threshold Sunday as the international Red Cross formally declared the conflict a civil war, a status with implications for potential war crimes prosecutions.

The Red Cross statement came as United Nations observers gathered new details on what happened in a village where dozens were reported killed in a regime assault. After a second visit to Tremseh on Sunday, the team said Syrian troops went door-to-door in the small farming community, checking residents’ IDs and then killing some and taking others away.

According to the U.N., the attack appeared to target army defectors and activists.

“Pools of blood and brain matter were observed in a number of homes,” a U.N. statement said.

Syria denied U.N. claims that government forces had used heavy weapons such as tanks, artillery and helicopters during the attack Thursday. Syrian Foreign Ministry spokesman Jihad Makdissi said the violence was not a massacre – as activists and many foreign leaders have alleged – but a military operation targeting armed fighters who had taken control of the village.

“What happened wasn’t an attack on civilians,” Makdissi told reporters Sunday in Damascus. He said 37 gunmen and two civilians were killed – a far lower death toll than the one put forward by anti-regime activists, some of whom estimated the dead at more than 100.

“What has been said about the use of heavy weapons is baseless,” Makdissi added.

The U.N. has implicated President Bashar Assad’s forces in the assault. The head of the U.N. observer mission said Friday that monitors stationed near Tremseh saw the army using heavy weaponry and attack helicopters.

The fighting was some of the latest in the uprising against Assad, which activists say has killed more than 17,000 people. Violence continued Sunday, with more clashes reported around the capital, Damascus.

The bloodshed appeared to be escalating. On Sunday, the International Committee of the Red Cross said it now considers the Syrian conflict a civil war, meaning international humanitarian law applies throughout the country.

Also known as the rules of war, humanitarian law grants all parties in a conflict the right to use appropriate force to achieve their aims. The Geneva group’s assessment is an important reference for determining how much and what type of force can be used, and it can form the basis for war crimes prosecutions, especially if civilians are attacked or detained enemies are abused or killed.

“We are now talking about a noninternational armed conflict in the country,” ICRC spokesman Hicham Hassan said.

War crimes prosecutions would have been possible even without the Red Cross statement. But Sunday’s pronouncement adds weight to any prosecution argument that Syria is in a state of war – a prerequisite for a war crimes case.

Previously, the Red Cross committee had restricted its assessment of the scope of the conflict to the hotspots of Idlib, Homs and Hama. But Hassan said the organization concluded that the violence was widening.