Syrian government forces have bombed the eastern edge of the capital Damascus in response to a surprise rebel assault.
The British-based Syrian Observatory for Human Rights says the army and allied forces have engaged in fierce clashes with opposition groups in and around the district of Jobar.
A major offensive is believed to have brought rebel fighters close to the heart of the Old City of Damascus, located near residential areas.
Syrian state media report the military has repelled an attack by what they call an al-Qaeda-linked group, saying "terrorists" had infiltrated the area through tunnels.
Having recaptured the key city of Aleppo last year, the Syrian government is pushing to break down all rebel control in Damascus and fully take back the city after six years of war.
Al-Jazeera's Mohammed Aljazaeri is in Syria and says the rebel attack is a major one.
"The attack is big and important, as it is near the capital Damascus. According to opposition sources, the attack began when two big trucks loaded with explosives were used on regime locations near Jobar district. Among those locations was the military operation room that the regime uses to direct its operations in Jobar and Eastern Ghouta. After the truck bombings, the opposition moved in, killing and arresting a number of regime soldiers. The opposition fighters approached Abaseen Square in Damascus and took control of parts of the power plant. If the opposition manages to progress further, it will be able to control the vital Adawi Highway, which will put them close to regime locations in the central part of the capital. The government forces have responded by fiercely targeting Jobar district with artillery and missiles, and there have been aerial raids by Syrian and Russian warplanes."
Weeks of air strikes had reportedly preceded the evacuation of people from the last rebel-held pocket in the northern city of Homs.
Homs was once known as a centre of uprisings against President Bashar Al-Assad, but it is now almost entirely under the control of government forces.
The Syrian Observatory for Human Rights says, under a government-backed deal, thousands of civilians and rebels are also expected to leave the al-Waer area within weeks.
Syria and Russian forces, alongside the Syrian Arab Red Crescent, are overseeing the process.
The evacuees are being transferred to the opposition-controlled areas of Azaz and Jarablus near the Turkish border.
Relief worker Hosain Darij says they will be housed in temporary tent camps.
"The manager of the camp told us that more than 200 families would arrive today from the areas around Homs. We will start to build more than 200 tents with water and washing facilities for our brothers who will be arriving from Homs."
Meanwhile, rebels and civilians have been pouring into Idlib, near the Lebanese border, from areas recaptured by government forces over the past year.
Now, a video has emerged online, purporting to show the aftermath of air strikes on Idlib.
The footage has not been independently verified.
In the video, members of what is said to be a civil-defence team are seen searching through the rubble of destroyed buildings.
A man identified as a rescue worker says survivors have been found.
"Warplanes targeted the governorate with four incursions, and we managed, thank God, to save seven children and a woman from under the rubble. Civil-defence teams are still searching for those who are trapped under rubble."
