The Britain-based Syrian Observatory for Human Rights said the explosion occurred at a garage near the Bab al-Salameh border crossing in the northern Syrian province of Aleppo. The garage is used by passengers who come to or leave the crossing point, said Rami Abdurrahman, the Observatory's chief.
Abdurrahman said it was not immediately clear if a suicide bomber caused the blast. He said those wounded were being treated in Turkish and Syrian hospitals. He said the dead included at least five women and three children.
In Turkey, a government official said 48 wounded Syrians were brought across the border for treatment and that 13 of them had died. Thirty-five of them were being treated in various hospitals near the Turkish-Syrian border, said the official, who spoke on condition of anonymity as he wasn't authorized to release information to journalists.
Such explosions have occurred in the past in border areas near Turkey.
Syria's conflict began with largely peaceful protests calling for reforms and transformed into an armed uprising and eventually a civil war following a ferocious military crackdown on protesters. More than 150,000 people have died since March 2011, and hundreds of thousands of people have been wounded.
"God, may you punish them!" a man could be heard shouting as people tried to put out a blaze consuming two vehicles with fire extinguishers. The video appeared genuine and corresponded with Associated Press reporting of the event. Explosions around Syria have killed and wounded thousands of people over the past years.