At least 20 people were killed in heavy airstrikes that targeted rebels trying to topple the regime in at least seven cities and regions. To underline their resolve, the government called on opposition fighters to surrender their arms and warned in cellphone text messages that the army is "coming to get you."
State television said the aim of the counteroffensive was to send a message to the opposition and its Western backers that President Bashar Assad's troops are capable and willing to battle increasingly better armed rebels on multiple fronts.
Rebels have been making gains in recent weeks, especially in the south near the border with Jordan. They have seized military bases and towns in the strategically important region between Damascus and the Jordanian border about 100 miles away.
However in the north, the main rebel stronghold, government troops have been chipping away slowly over the past weeks at rebel gains around the city of Aleppo, the country's main commercial hub. They have been hammering rebel-held districts inside the city with fighter jets and artillery, sowing fear among residents.
Troops recaptured on Saturday the village of Aziza on a strategic road that links Aleppo with its airport and military bases, activists said. Rebels have been trying to capture that airport and the nearby bases for months now.
The regime seized back the village southeast of Aleppo after a 10-day battle with rebels, said Rami Abdul-Rahman, director of the Britain-based activist group Syrian Observatory for Human Rights.
"It's a setback for the rebels because the village is an important strategic point from which the army can shell (opposition) positions all around the area," Abdul-Rahman said.
It's also an outpost from which the army will be able to protect its convoys traveling the highway to ferry supplies to its bases at the airport.
Over the last year, rebels have greatly expanded the territory they hold in the northeastern provinces, including Idlib and Aleppo along the Turkish border.
In February, they extended their control into Raqqa province in the northeast, seizing the second hydroelectric dam on the Euphrates River. Last month, the rebels captured Raqqa's provincial capital of the same name -- the first city to fall entirely under opposition control in the 2-year-old conflict.
Capturing Aleppo's airport would be a major strategic victory that would enable the opposition to receive aid flights.
Aziza is one in a string of settlements along the Aleppo airport road that government troops have taken back.
The base inside the airport complex includes an airstrip from which regime fighter jets have been taking off to bomb targets around the country.
Sunday's airstrikes targeted Aleppo, the central cities of Homs and Hama and the city of Idlib in the north near the Turkish border. The western Mediterranean city of Latakia, and the eastern province of Deir el-Zour and the suburbs of the capital Damascus were also targeted.
Anti-government activists in Aleppo posted videos on line, showing the aftermath of Saturday's airstrike on what they say is Sukkary district in the northern city. Dozens of residents are standing on piles of rubble in front of a row of residential buildings, looking in disbelief at the front of the building that was blown off when a missile slammed into it.
In another video, men help a woman climb down from a balcony of the second floor of a building that has partially collapsed after a missile ripped through it.
The videos appear consistent with AP reporting from the area.
State television said the primary goal of the airstrikes was to "recapture areas taken by the terrorists," the term the regime uses to refer to opposition fighters in the civil war.
Regime fighter jets pounded villages in rebel-held areas in Latakia province before. But they do not frequently hit the city of the same name that is mostly populated with Syrian minority communities including many members of the Alawite sect, an offshoot of Shiite Islam that Assad and his family belong to.
The rebels and opposition supporters are mostly Sunni Muslims, a majority in Syria.
The Aleppo strike was the deadliest air raid on Sunday, killing up to 12 people, according to another anti-regime activists group, The Local Coordination Committees.
In other violence, a man was shot and killed by an army sniper in the southern city of Daraa, the Observatory said, adding that clashes between troops and rebels raged in the opposition strongholds around Damascus. At least 15 people were killed in the fighting around the capital, the group said.
Daraa province has been the scene of fierce fighting in recent weeks, with rebels making gains in the province and further south.
Last week, they looked poised to take over the area along the Jordanian border, which could be used to try to stage an attack on Damascus, Assad's seat of power.
Abdul-Rahman said there was little rebel advancement in the province on Sunday, despite rebel forces receiving heavier flows of weapons through Jordan as well as training there by the U.S. and other countries.
In Istanbul, U.S. Secretary of State John Kerry met with Turkish Foreign Minister Ahmet Davutoglu on the first leg of a 10-day overseas trip. They discussed shared U.S. and Turkish efforts to support Syria's opposition groups, which have struggled to unify and strengthen links with rebels on the battlefield.
"The United States and Turkey will continue cooperating toward the shared goal of a peaceful transition in Syria," Kerry said.
More than 70,000 people have died in the conflict that began in March 2011.
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