The Britain-based Syrian Observatory for Human Rights said seven rebels were killed in the attack on the air defense base in the town of al-Safira.
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The Observatory's chief Rami Abdul-Rahman said that al-Safira, just south of Syria's largest city, Aleppo, is home to Syrian military factories.
He said the plants are surrounded by army bases and posts to protect them.
Friday's clashes come three days after rebels captured a warehouse in the area. It was later bombed by Syrian warplanes, killing nearly two dozen rebels, Abdul-Rahman said.
The conflict in Syria that began in March 2011 and became a civil war has left more than 40,000 people dead.
NATO chief Anders Fogh Rasmussen on Friday condemned Syria's firing of short-range missiles after a NATO source said allied surveillance had detected new launches of Scud-type missiles in Syria this week.
The source said there had been multiple launches of the missiles inside Syria on Thursday morning, more than a week after the alliance first detected Scuds being fired during Syria's 21-month-old civil war.
Rasmussen said NATO strongly regretted the missile launches. "I consider (them) acts of a desperate regime approaching collapse," he told reporters at NATO headquarters.
On Thursday, the UN General Assembly condemned human rights violations in Syria, Iran and North Korea and demanded an immediate halt to actions ranging from attacks on civilians to torture and restrictions on freedom of movement.
The 193-member world body voted 135-12 with 36 abstentions Thursday for a resolution demanding an immediate end to "widespread and systematic" gross human rights violations by Syrian authorities.
It approved a resolution calling for an end to Iran's continuing use of torture, the death penalty and execution of minors by a vote of 86-32 with 65 abstentions.
For the first time, the assembly approved a resolution targeting human rights violations in North Korea by consensus. It expressed serious concern at the North's "systematic, widespread and grave violations of civil, political, economic, social and cultural rights."
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