Meanwhile, the Observatory said members of Jabhat al-Nusra blew themselves up in two car bombs outside an intelligence office in the northeastern city of Shadadah, killing at least 14 security agents and wounding many people.
The Observatory said Shadadah has been witnessing heavy clashes between troops and rebels.
Jabhat al-Nusra, which led the fighting at the dam, has been named by the U.S. government as a terrorist organization. It has proved to be the most effective group among rebels fighting in Syria.
Also in northern Syria, a car bomb exploded at a border crossing with Turkey in Idlib province. Turkey’s prime minister, Recep Tayyip Erdogan, said 13 people died in the blast. He didn’t specifically say the explosion was caused by a bomb, possibly in deference to an ongoing investigation, but he left little doubt that authorities believed it was the work of assailants.
‘‘The incident is very important in showing to what extent our stance on terror and our sensibility toward Syrian incidents is well-directed,’’ Erdogan said.
The border area between the two countries has seen fierce fighting in the civil war. Tensions have also flared between the Syrian regime and Turkey in the past months after shells fired from Syria landed on the Turkish side.
As a result, Germany, the Netherlands and the United States decided to send two batteries of Patriot air defense missiles each to protect Turkey, their NATO ally.
Associated Press writers Chris Torchia in Istanbul and Ezgi Akin contributed in Ankara, Turkey contributed to this report.