Northern Syria (CNN) -- Violence flared yet again around Syria on Saturday, with the opposition reporting outright executions around Damascus and voicing fears about a climactic battle for the city of Aleppo as regime forces approached.
Free Syrian Army fighters told CNN that two large columns of government troops were heading toward Aleppo, the Middle East nation's most populous city. One is moving from Latakia on the Mediterranean coast and the other from Damascus.
Mohamed Said, a spokesman in Aleppo for the Syrian Revolution General Commission, said late Saturday that members of the opposition Free Syrian Army are trying to head off some of the approaching troops by attacking them in Idlib province.
Fighting in the northern Syrian city has raged for days, causing widespread destruction and casualties and forcing tens of thousands of civilians to flee. The addition of thousands of more troops to the mix, and even bloodier battles to follow, has fueled worries within the rebel ranks and around the world.
In remarks Friday to the U.N. General Assembly, Secretary-General Ban Ki-moon voiced concern the situation may get even worse, saying the "ancient and storied" city is now "the epicenter of a vicious battle between the Syrian government and those who wish to replace it."
Rebels in Aleppo exude gritty confidence and possess growing clout. They say they control significant parts of the city and are working to wrest control of the entire sprawling metropolis from the much larger, better equipped forces of Syrian President Bashar al-Assad.
The regime reported deaths, injuries and the capture of dozens of "terrorists" -- the term it commonly uses for opposition fighters -- in several neighborhoods of Aleppo on Saturday. Opposition activists, meanwhile, said al-Assad's forces had unleashed persistent and powerful bombs and shelling, while rebels have launched their own attacks in multiple neighborhoods.
That includes a brazen push Friday to seize a state-run broadcasting building in Aleppo. Rebels pushed into the radio and TV complex and took over parts of it, before eventually withdrawing because of snipers and military shelling, the opposition Local Coordination Committees of Syria said.
The regime reported "a large number of terrorists killed and injured during their attempt to storm" the building. Free Syrian Army commanders say the broadcasts can no longer emanate from the site, because of bombardment by Syrian aircraft. A rebel flag has been planted atop the building, they added.
Elsewhere in Aleppo, in Khan al-Assal neighborhood, the state-run Syrian Arab News Agency reported regime forces had caused the deaths and injuries of "a big number of terrorists" and confiscated weapons.
Rebel fighters, though, offered a different take. Mustafa Abdallah, a Free Syrian Army commander, claimed his group's fighters killed a few dozen Syrian soldiers in a two-hour gunbattle and captured eight others. At least one rebel fighter died, he said. Rebels eventually retreated as helicopters shelled the area and military reinforcements advanced, Abdallah said.
The Local Coordination Committees of Syria also noted "fierce clashes" in the Meridien neighborhood as warplanes fired on the area.
Syria's civil war is hardly confined to Aleppo, however.
At least 145 people were killed across the country Saturday, according to the LCC.
Some of the worst bloodshed was in Damascus, especially the Tamadon neighborhood. The LCC reported that 12 people there -- out of 53 killed throughout the city, including four others "executed" in the Qazzaz neighborhood -- were "summarily executed" after prayers by government forces.
Syrian state-run TV, by contrast, featured a banner Saturday night that read: "Our valiant armed forces cleanse Tadamon neighborhood in Damascus entirely from the remnants of mercenary terrorists."
Susan Ahmed, a spokeswoman for the Syrian Revolution, said Free Syrian Army forces pulled out of the neighborhood "tactically to protect civilians."
Even so, she added that there had been fighting, shelling and fatalities throughout the day and throughout Damascus, including in areas around parliament, the president's residence and the main building for al-Assad's cabinet.
"Very high and violent" explosions continued to pierce the nighttime air early Sunday, as did persistent gunfire, she said.
Elsewhere around Syria's capital, "armed terrorists" attacked a bus carrying 48 Iranian Shiite pilgrims and kidnapped them, Iranian state media said. Syrian state-run media also reported the bus abduction and said it is under investigation.
It is not known if the hijacking is linked to the resistance against the Syrian government. The Iranian government is an ally of the al-Assad regime, which has been fighting a rebel movement dominated by Sunnis. Iranian Foreign Minister Ali Akbar Salehi called his Turkish counterpart, Ahmet Davutoglu, asking for that nation's "prompt intervention" to assure the pilgrims' release, Iran's state-run Islamic Republic News Agency reported.
The Local Coordination Committees said at least another 21 died in the province of Deir Ezzor, 15 in Hama and 21 in Aleppo, though it is not known how many of those latter deaths occurred in Khan al-Assal.
The Syrian government also acknowledged widespread deaths Saturday in several places including the provinces of Deir Ezzor, Hama, Idlib and Homs, plus Damascus and its suburbs. It said it killed and injured many people it labeled "terrorists."
Roughly 17,000 people have died since the Syrian conflict first flared in March 2011, when government forces began cracking down on protesters, Ban said last month. Opposition activists put the toll at more than 20,000.
The violence has intensified during Muslims' holy month of Ramadan, which began July 21 in Syria and ends later this month, the Red Cross said.
Hundreds of thousands have fled their homes in the fighting, though many more remain. Some have found temporary homes in makeshift shelters, including in 12 schools in and around Damascus and several others in Aleppo. The Red Cross said it's been working with the Syrian Arab Red Crescent to deliver food and other necessities for more than 52,000 people in the country.
On Friday, a myriad of diplomats rebuked the regime at the U.N. General Assembly in a resolution that noted "human rights abuses by armed opposition groups" but reserved most of its ire for al-Assad's regime. It condemned "the continued widespread and systematic gross violations of human rights and fundamental freedoms by the Syrian authorities and pro-governmental militias."
The resolution also reiterated diplomats' "call for an inclusive Syrian-led political transition to a democratic, pluralistic political system."
The Saudi-sponsored resolution passed by a 133-12 vote, with 31 abstentions. Such General Assembly resolutions are legally non-binding, unlike Security Council resolutions, though diplomats hope it spurs tougher, more definitive action on Syria.
So far, Russia and China have blocked tough council resolutions against the regime, including more widespread sanctions.
China, one of the nations to vote against the resolution, defended its stance on Saturday.
Wang Kejian, deputy director general at the Chinese Foreign Ministry, said China "is opposed to any action forcing a regime change in Syria and sanctions can only make the situation more complicated."
"Solutions imposed from outside do not help solve the crisis," he said.
CNN's Ben Wedeman and Kareem Khadder in northern Syria and Samira Said, Amir Ahmed, Saad Abedine and Hamdi Alkhshali in Atlanta contributed to this report.