(CNN) -- Syrian forces killed at least 38 people in a Damascus suburb Sunday, opposition activists said, as the government said it "cleansed" the area of terrorists.
"Units of the armed forces cleansed al-Hameh and Qudsayya areas in Damascus countryside of armed terrorist groups, declaring them safe areas," the state-run Syrian Arab News Agency reported Sunday.
But opposition members painted a different picture of al-Hameh, saying forces loyal to President Bashar al-Assad "carried out a massacre in the city." The bodies of 38 people were found "field-executed," reported the Local Coordination Committees of Syria, a network of opposition activists.
They were among the at least 121 people killed nationwide Sunday, according to the LCC, as the Syrian civil war rages in its 19th month.
CNN is unable to independently confirm reports of casualties or violence because the Syrian government has restricted access by international journalists.
In the beleaguered province of Homs, warplanes reportedly shelled a water plant in the city of Qusair, the opposition Local Coordination Committees of Syria said.
Less than an hour later, the LCC said the rebel Free Syrian Army shot down a warplane in Qusair.
Rebel fighters surround Syrian base near Turkish border
After a fifth straight day in which Turkish and Syrian forces exchanged fire, rebel fighters moved under the cover of night Sunday to attack a military camp in the northern Syrian town of Tal Abayad, a witness and fighter said.
Suspecting "low morale" among Syrian soldiers, the opposition fighters attacked and surrounded the military post and its estimated 150 troops about 10 kilometers (6.2 miles) from the Turkish border around 7 p.m. (noon ET). They remained stationed outside the camp early Monday morning, by which time the opposition claimed to have destroyed three tanks.
"We feel very strongly we will take it over in the next few hours," rebel fighter Abu Abdallah told CNN.
He and Ayham Khalaf, an eyewitness an activist, said government forces have been shelling the surrounding area -- including firing mortars that fell into Turkey -- from the Tal Abayad camp. If they take it over, the opposition fighter said that its forces will control an area that extends 45 kilometers (28 miles) south of the Turkish border.
That cross-border shelling continued Sunday, with one shell hitting near a Turkish government agriculture office in Akcakale, Turkey, where five Turks were killed four days ago.
Mayor Abdulhakim Ayhan told Turkey's semi-official Anadolu News Agency that Syrians fired the mortar shells from Tal Abyad, with one hitting near the Office of Soil Products.
Witness Salih Aydogan said no one was injured, but the shell fell very close to town. As he spoke with CNN, Turkish military fired two more shells at Syria.
"We heard (the Turkish military) fire back immediately. They retaliated with two shots," said Aydogan. "We just got lucky this time."
Commander claims rebels overrun military checkpoints
The Free Syrian Army captured a battalion leader and took control of three checkpoints in the border town of Badama, deputy commander Col. Malik al Kurdi told CNN Sunday.
Al Kurdi said the rebels stormed a battalion-sized force and only a small group of soldiers remains in the city. Badama is near Syria's border with Turkey but further west than where the shelling occurred, located about 80 kilometers east of the Mediterranean Sea port city of Latakia and about 350 kilometers west of Tal Abyad.
"We pushed them back and captured a lot of them, destroyed a lot of the machinery and the vehicles they were using," he said. One of the soldiers he claimed they captured was the colonel who led the Syrian force.
Elsewhere in Syria -- including in the cities of Hama and Deir Ezzor, as well as the Damascus suburb of Mleiha -- Free Syrian Army fighters clashed with Syrian troops, according to the LCC.
Heavy shelling and gunfire from government forces occurred in many other locales, such at Taftanaz in Idlib province and Ghanto in Homs province.
Aleppo was also a hub of activity, with the opposition group reporting shelling in the Bustan al-Qasr and Sakhour neighborhoods. The LCC also said that 20 Syrian soldiers from a single regiment defected to join the rebels in Aleppo, Syria's commercial hub and most populous city.
CNN's Amir Ahmed, Ivan Watson and Gul Tuysuz contributed to this story.