Forces loyal to the Syrian President Bashar al-Assad are advancing in rebel-held parts of the central city of Homs, both the opposition and state media have said.
Homs-based activist Tarik Badrakhan said on Saturday that Syrian troops seized control of buildings in the opposition-contolled district of Khaldiyeh, the first time government forces entered Homs neighbourhoods held by rebels for over a year.
Syrian state media said troops were advancing and they had killed rebels in the area.
Badrakhan said troops began to advance on Friday night.
Homs is a strategic city located between the capital Damascus and the Syrian coast, a stronghold for the Assad regime.
Homs, considered the "capital of the revolution", has paid an enormous human and material price for the uprising against Assad's regime that began in March 2011 and has since evolved into fully-fledged civil war.
Activists claim that fighters from Lebanon's Hezbollah Shia armed movement, which has sided with Assad's forces, have been battling rebels in the city.
Hezbollah fighters helped the Syrian army capture Qusayr, a key town near Lebanon's border last month, dealing a blow to opposition fighters who have been ferrying supplies and fighters over the border.
Elsewhere on Saturday, Syrian warplanes launched a series of strikes on the outskirts of Damascus.
"Warplanes carried out several air strikes on the edges of Assali [in the south] and Qaboon (east)," said the Britain-based Syrian Observatory for Human Rights.
The Observatory also reported fresh clashes in Assali as well as in the southwestern neighbourhood of Qadam, adding that the army shelled rebel-held Yarmouk in the south and Jobar in the east.
Air strikes also targeted other rebel areas east of Damascus, among them rebel bastion Zamalka, said the group.
Central Damascus is still squarely in army hands.
The latest reports of violence came just as the opposition Syrian National Coalition voted on to elect a new leader.
The top two candidates, however, failed to gain a simple majority needed to become president of the Coalition.
A runoff ballot was scheduled for later on Saturday after Ahmad Jarba, a tribal figure linked with Saudi Arabia, and Mustafa al-Sabbagh, a businessman who is Qatar's point man, did not gain more than half of the votes in the 115 member Coalition in an early morning ballot in Istanbul.
The Coalition has been without a leader for months after its head quit over disagreement over potential talks with Assad's government.