An explosion on a minibus near the Cilvegozu border post on the Turkish side of its border with Syria has killed 13 people.
"It was a powerful explosion. But whether this was a vehicle laden with explosives or another type of explosion, I think, at the latest, will become clear tomorrow," said Turkish deputy prime minister Bulent Arinc.
"All possibilities are on the table, including political motives."
The explosion comes as Syrian rebel groups took control of a strategic hydroelectric dam, which provides electricity to Aleppo.
Syrian President Bashar al-Assad on Monday stressed that he would not resign, "no matter how pressures are building up", state-run Sana news agency reported.
"Syria will remain the beating heart of the Arab world and will not give up its principles despite the intensifying pressure and diversifying plots not only targeting Syria, but all Arabs," he said.
