Syrian government troops Saturday launched an attack on rebel-held areas in the central province of Homs, activists and state media reported, dpa informed.
"The regime army is launching an air and ground attack on the areas of Khaldiyeh, Bab Hud, Hamidiyeh and Bustan al-Diwan," activist Omar Homsi said.
"The airstrikes are a cover for the start of the ground attack," he said.
Homs is Syria's third-largest city and one of the first to have joined the revolt against President Bashar al-Assad when the uprising started in March 2011.
This month, al-Assad's regime, backed by fighters from the Lebanese Shiite Hezbollah movement, retook the strategic town of al-Kussair in Homs from the rebels.
Rami Abdel-Rahman, the head of the pro-opposition, Britain-based Syrian Observatory for Human Rights, confirmed Saturday's onslaught.
"Regime troops are trying to storm Khaldiyeh, and fighting is under way around the old city of Homs," he said. "Tanks and at least seven buses packed with regime soldiers have arrived at an area near the entrance of Khalidiyeh."
Abdel-Rahman added that Khaldiyeh and the old city have been under siege by the army for about a year.
Syrian state television aired footage of troops near Khalidiyeh and said government forces were making "advancements in the area."
The state news agency SANA, meanwhile, said the army had dismantled a large number of explosive devices planted by what it called "terrorists" in Khalidiyeh.
At least 93,000 people have been killed in Syria's 27-month conflict, according to the United Nations.
In neighbouring Lebanon, two people were killed Saturday and six wounded in clashes in the northern city of Tripoli between opponents and supporters of the Syrian government, Lebanese police said.
Violence has repeatedly broken out in Tripoli, a mostly Sunni city, between Sunni residents who back the Syrian opposition and the minority Alawites, a Shiite sect to which al-Assad belongs.