SARMADA, Syria, May 6 (UPI) -- Airstrikes on a Syrian refugee camp that killed dozens of civilians "could amount to a war crime," a senior United Nations official said Friday.
Stephen O'Brien, the UN under-secretary for humanitarian affairs, said, "If this obscene attack is found to be a deliberate targeting of a civilian structure, it could amount to a war crime."
The airstrikes Thursday were near Sarmada, a town in Idlib province just 12 miles from Reyhanli in Turkey.
The United States said it has not confirmed who struck the camp.
"We don't know yet if it's Syrian or Russian aircraft, but they struck in the middle of the camp and many of the tents have been burned," said Alaa Fatraoui, a journalist who saw the aftermath.
Syria and Russia have denied any involvement.
"Russia and the Russian Aerospace Forces in Syria act with utmost responsibility in Syria in order not to damage the fragile atmosphere of truce," Russian presidential press secretary Dmitry Peskov told journalists on Friday. "Russia has repeatedly demonstrated this and calls on all other sides to share this responsible and cautious approach."
"There is no truth to reports... about the Syrian air force targeting a camp for the displaced in the Idlib countryside," the Syrian military said in a statement on Friday carried by state media.
Zeid Ra'ad al-Hussein, the high commissioner for human rights, said the tents were highly visible from the air, the Guardian reported, so it was "extremely unlikely that these murderous attacks were an accident."
"My staff, along with other organizations, will leave no stone unturned in their efforts to research and record evidence of what appears to be a particularly despicable and calculated crime against an extremely vulnerable group of people," he said.
The French foreign ministry also issued a statement saying the attack could constitute a war crime.
"The perpetrators must be held accountable and brought to justice," the statement read. "France calls for an impartial and independent investigation to be carried out in order to shed full light on this heinous act."
The White House said there was "no justifiable excuse" to target civilians, White House spokesman Josh Earnest said.
"These individuals are in the most desperate situation imaginable, and there is no justification for carrying out military action that's targeting them," Earnest said.
The opposition's Syrian National Coalition described the attack as an "appalling massacre by regime forces against civilians."
The Syrian Observatory for Human Rights, a monitoring group, said victims included children.
The al-Kammouneh camp had about 500 tents. They had fled the nearby Aleppo province.
A cease-fire had been brokered by the United States and Russia but talks had been deadlocked.
When asked if the bombing would jeopardize negotiations, Peskov said that "it's a matter of facts, if there were no Russian planes and they did not operate there, then it's another wave of disinformation."