A massive car bomb ripped through a crowded garage Thursday near an opposition-held border crossing between Syria and Turkey, killing at least 43 people, an anti-government activist group told The Associated Press.
The attack came as President Bashar al-Assad's forces have seized the momentum of the country's three-year-old civil war ahead of presidential elections scheduled for June 3.
The Britain-based Syrian Observatory for Human Rights said the blast killed 43 people and wounded more than 80. Injured Syrians who were taken to hospitals in Turkey and later died are among the 43 killed, said Rami Abdurrahman, the head of the Observatory. The group relies on a network of activists on the ground to compile its findings.
The Local Coordination Committees, another activist group, also reported the car bombing but said only that it killed and wounded "dozens of people."
Car bombings have become common in Syria as the influence of armed opposition groups has risen, dampening the support of the United States and its European allies for the opposition seeking to oust Assad.
Opposition activists have blamed Al-Qaeda-linked fighters for previous attacks in the region, but so far no group has claimed responsibility for Thursday's blast.
An amateur video posted online showed women, men and children at the scene of the blast near the Bab al-Salameh border crossing in the northern province of Aleppo. In another video posted online by activists, burned-out cars are seen in the area as people walk past pools of blood, with clothes and other personal belongings scattered around.
"Oh God, may you punish them!" a man shouted as people used fire extinguishers to put out flames consuming two vehicles.
In Turkey, a government official said 94 wounded Syrians were brought across the border for treatment and that 14 of them had died.
The garage where the explosion took place stores cars that people hire to take them across the border.
Opposition forces fighting Assad captured the Syrian side of the border crossing in July 2012, opening a key transit point for people and supplies. But the area has seen an increase in clashes and attacks between oppostion groups fighting for control of the crossing in recent months.
The Syrian conflict started as largely peaceful protests against Assad's rule and turned into civil war after some opposition supporters took up arms to fight a government crackdown on dissent. Activists say more than 150,000 people have been killed and millions have been driven from their homes, seeking shelter in neighboring countries and in safer parts of Syria.
Thursday's attack came as U.S. Secretary of State John Kerry said the U.S. and other nations supporting the Syrian opposition agree that the planned election is a "farce" because it excludes Syrians who have been displaced by fighting. Kerry said he and his counterparts from 10 other nations agreed to ramp up what can be done to assist the Syrian opposition. But he stopped short of promising any U.S. military aid.
Meanwhile, government forces pressed on with their campaign to push opposition forces from the areas that could threaten Damascus, the seat of Assad's government, dropping bombs from a helicopter Thursday on the village of Tal Shihab and killing nine people, the Observatory said.
On Wednesday at least 20 government soldiers were killed in a massive bombing after rebels detonated a tunnel packed with explosives under a military base in the Wadi Deif area of the northwestern province of Idlib.
Al Jazeera and wire services