The Free Syrian Army has sacked its leader with the Western-backed rebels suffering repeated setbacks, amid signs of an escalation in fighting.
Activists warned on Monday regime troops were preparing a ground offensive against Yabrud, the last rebel-held stronghold in the strategic Qalamun region near the Lebanon border, after days of aerial bombardment.
On the diplomatic front, US Secretary of State John Kerry has slammed Russia for "enabling" Syria's President Bashar al-Assad to stay in power, after Geneva peace talks broke off on Saturday without result.
Moscow is dismissing the allegation and accuses the United States of failing to ensure a "truly representative opposition delegation" attended the talks.
The sacking of rebel military commander Selim Idriss was announced on Sunday by the FSA, which said he was being replaced by Brigadier General Abdelilah al-Bashir, another army deserter.
Colonel Qassem Saadeddine of the rebel coalition said the decision was taken because of "the paralysis within the military command these past months" and the need to "restructure".
But Aron Lund, editor of the Carnegie Endowment's Syria in Crisis website, said he suspected there was more to the decision.
"It appears Idriss may have been blocking a Saudi-backed plan to revamp" the FSA's Supreme Military Council, said Lund.
Saudi Arabia has been a leading provider of military support to the Sunni-led rebels in a bid to counter the regional influence of Shi'ite Iran, a key ally of the Assad regime.
The FSA has taken a beating in recent months not only from regime forces but also from Islamist fighters who have joined the battle to unseat Assad.
Considered the "moderate" rebel group, the FSA was once Syria's strongest armed opposition force but is now increasingly marginalised by Islamists, including al-Qaeda-inspired groups.
The official SANA news agency said the army on Monday recaptured an Alawite village in central Hama province where rebels "massacred" civilians earlier this month.
In the Damascus area, meanwhile, a local truce went into effect in the southern suburb of Babbila, the latest in a series of local ceasefires in flashpoints around the capital.
An AFP reporter who visited the area under official escort said talks are taking place to arrange similar agreements in other areas.
But analysts say with the failure of the latest round of peace talks, the regime and rebels are likely to ratchet up military operations.
"It will probably get worse before it gets better," said Volker Perthes, director of the German Institute for International and Security Affairs.
"Both sides will try to show that they can change the balance on the ground in their favour, and that they aren't forced to negotiate out of weakness."
The Syrian Observatory for Human Rights, a Britain-based monitoring group, reports a surge of fighting around Yabrud, on a strategic highway linking Damascus and the central city of Homs.
Spokesman Rami Abdel Rahman says Syrian warplanes dropped explosive-packed barrels on the town's outskirts, and that fighting erupted in the nearby rebel-held towns of Ras al-Maara and Al-Sahel.
The Observatory has meanwhile updated the toll of a Friday car bombing in the southern Daraa province to 49, including four children.
