Syrian forces have been bombing and shelling from a distance but have been unable to dislodge opposition fighters holed up in devastated neighborhoods. Retaking Aleppo and Homs could give the regime some breathing room.
In Aleppo, government forces gained some ground in recent house-to-house combat, according to an Associated Press journalist in the city.
On Saturday, government troops captured the city's Sakhour roundabout after days of heavy fighting, a Syrian official said on condition of anonymity because he was not authorized to speak to the media.
Heavy shelling also was reported in Taibeh, a town near Homs, an early center of the uprising. Opposition activists said at least 10 people were killed and dozens were wounded.
Amateur video from Taibeh, posted Saturday, showed several badly disfigured bodies being pulled from the back of a pickup truck by distraught bystanders. One body was carried away on a red stretcher.
In another video, masked rebel fighters posed with assault rifles in what they said is an air defense base east of Damascus they captured earlier in the week.
The video showed captured weapons, including anti-aircraft missiles, heavy machine guns and large-caliber ammunition. The rebels surrounded a group of captured regime soldiers. The captives, some with bandages on their heads, each stood up and gave their rank and name.
The authenticity of such videos cannot be confirmed independently because Syria imposes tight restrictions on foreign journalists.
In a success for the opposition activists said, rebel fighters took control of the village of Khirbet el-Jouz in Syria's northwestern Idlib province, about 10 miles from the Turkish town of Guvecci.
Turkey's state-run Anadolu Agency said that rebels planted their flag on the roof of a building that had been used as a base by regime troops in the village. The takeover came after intense clashes, with mortar shells exploding at a relentless pace, some near the Turkish border, Anadolu said.
Two of the mortars from that battle landed in Turkey, and a third shell hit later in another village in Turkey's Hatay province. No casualties were reported, but Turkish forces returned fire each time, according to Anadolu and the Hatay governor's office.
Earlier this week, Turkey's parliament approved such retaliation, expanding Turkey's response options. Turkey's leaders have reiterated that they don't want war with Syria, but another dramatic or deadly border incident could force unwanted escalation.
In another international entanglement, Assad ally Iran appealed to rebel backers Turkey and Qatar to help release 48 Iranians purportedly being held by Syrian rebels since August.
In amateur video posted late Thursday, rebels threatened to kill the captives by the end of the weekend unless the regime halts military operations against the opposition.
Iran's Foreign Minister Ali Akbar Salehi spoke by phone Saturday with the Qatari prime minister and the Turkish foreign minister and received assurances they would try to help, Iran's state news agency IRNA reported.
Iran says those abducted were pilgrims visiting a Shiite shrine in Damascus. The Syrian opposition claims they are members of the elite Revolutionary Guard helping the Syrian regime.