An eyewitness to the attack told The Daily Star that he believed at least 14 people were killed by the explosion at the Bab al-Salameh crossing, with around 60 people taken in ambulances to the southern Turkish city of Kilis for treatment.
The man, who declined to give his name, said that a large number of the wounded were children, and had severe injuries.
“It was a taxi that had crossed the Syrian border post and was parked on a main road, where cars and buses are lined up waiting to get across to Turkey,” he said. “The taxi detonated before it reached an inspection point.”
A Turkish border official said the blast near Turkey’s Oncupinar border post, which sits opposite the Syrian Bab al-Salameh gate, could be felt several kilometers away.
Abu Osama, a camp administrator, told AFP that the explosion happened behind his office and at least 20 tents were reduced to rubble. “Some of the bodies and tents melted from the explosion,” he said. “We have had thousands of new refugees come to this area the past 20 days because of the barrel bombing in Aleppo.”
He blamed the attack on militants from ISIS and said it had fired several rockets near the camp over the past few days where members of the rival Islamic Front rebel group are based.
The eyewitness agreed that ISIS was likely behind the blast at the camp , which he said was home to approximately 20,000 people.
“Last night, ISIS was firing tank shells near the camp. After the explosion, there were clashes nearby, between ISIS and the Islamic Front,” the eyewitness said.
The Britain-based Syrian Observatory for Human Rights monitoring group said at least five people were confirmed dead and a fire broke out in the camp after the blast, while the Anadolu Turkish agency gave a death toll of 10. Pro-opposition news websites put the death toll at 50, with dozens of wounded.
Thousands of Syrians have been fleeing the city of Aleppo, some 60 kilometers south of Kilis, in recent weeks because of a campaign of improvised “barrel bomb” attacks  by President Bashar Assad’s forces.
Many of the displaced live at a makeshift camp on the Syrian side of the border. Thursday’s blast hit this area, according to video footage.
In Syria, rebels were engaged in fierce battles with regime forces trying to capture the town of Yabroud, their main stronghold in the strategic Qalamoun region near the Lebanese border, the Observatory said.
Meanwhile, in the city of Aleppo, eight soldiers were killed by a rebel suicide bombing at the city’s central prison, which rebels have long been trying to capture, the Observatory said. And 18 rebel fighters were killed when they launched a dawn assault against an Alawite village in central Homs province.
The Observatory said rebels were fighting on Yabroud’s outskirts against government troops, backed by National Defense Forces militia and Lebanon’s Hezbollah.
The rebel side included Islamist brigades and the Nusra Front, an Al-Qaeda affiliate, the Britain-based Observatory said.
“There have been many losses on both sides, but there are not exact figures yet,” the Observatory said, adding that a citizen journalist with the rebels was among those killed.
“Yabroud will be taken by the Syrian army very soon, by force or through negotiations. Then the mountain leading to the village of Arsal [in Lebanon] will be taken.” Syria’s Al-Watan newspaper said the “army is advancing around the town and is ready to take control,” with a security source telling AFP the plan was to advance incrementally on all sides of the town “until it is taken completely.”
The battle is crucial for Hezbollah, which says most of the vehicles used in recent car bombing of its strongholds in Lebanon have come from Yabroud, which lies just over the border.
Yabroud was once home to some 30,000 residents, around 90 percent Sunnis and 10 percent Christian.
It has been a rebel stronghold since early in the uprising that began in March 2011, and is now the only key town remaining under opposition control in the Qalamoun region after a regime advance last year.
In central Homs, the Observatory said 18 rebels were killed after launching a dawn raid on Al-Qumeiri, an Alawite village. Troops and members of the National Defense Forces militia pushed the rebels back, the group said.
In Aleppo, meanwhile, the Observatory said eight soldiers were killed and 20 wounded in a triple suicide bombing by the Nusra Front.
It said a car exploded at the entrance to the prison and two suicide bombers blew themselves up inside the facility, after which Syrian army aircraft began bombing the area around the prison.