Regime forces backed by Hezbollah now control half of the Khaldiyeh district of Homs after ousting rebels in fierce fighting in the central Syrian city, a watchdog said on Saturday.
"Loyalist forces backed by fighters from Hezbollah have advanced over the last 24 hours and now control 50 percent of Khaldiyeh," the Syrian Observatory for Human Rights said.
Its chief Rami Abdel Rahman told AFP on Saturday that overnight, "there was continuous heavy mortar and artillery fire" and that the rebel district was still being pounded.
He said rebels were putting up "fierce resistance" amid "very intense clashes".
Militant network the Syrian Revolution General Commission also reported heavy fighting in the district that has been besieged by regime forces for more than a year.
"Khaldiyeh is being targeted by an uninterrupted heavy bombardment, and on the ground there is fierce fighting between Free Syrian Army fighters and regime forces backed by Lebanon's Hezbollah trying to take the district," an SRGC statement said.
It and the Observatory both said the Old City district of Homs -- dubbed the "capital of the revolution" against President Bashar al-Assad -- was being pummelled too.
The latest regime offensive on besieged rebel-held neighbourhoods of Homs is now in its fourth week.
Government forces are seeking to secure another victory like the one in Qusayr near the border with Lebanon in June, when Hezbollah was key in retaking the strategic town.
Hezbollah, the most powerful military force in Lebanon and a staunch ally of the Assad regime in Syria, has had its military wing blacklisted by the European Union as a terrorist group.