The Syrian army backed by Hezbollah fighters bolstered its positions in the embattled opposition stronghold of Qusayr on Saturday, as rebels prepared for a renewed assault, raising fears for trapped civilians.
The opposition Syrian National Coalition issued a statement saluting rebel fighters in the town, including new battalions that have arrived in recent days.
And in Lebanon, the conflict spilled over, with rocket fire once again landing in the eastern Bekaa region.
"There are ongoing clashes in northern Qusayr, and the opposition fighters are fighting with everything they've got," Rami Abdel Rahman, director of the Syrian Observatory for Human Rights watchdog, told AFP.
"Regime forces are reinforcing the sites that they have north of the city, including Dabaa airport and Jawadiya," he added.
The group said at least 15 tanks were massed at government-held points north of Qusayr, which is considered a key strategic prize by both the regime and the rebels.
It sits on the route between the capital Damascus and the coast, and lies near the Lebanese border, providing a key rebel conduit for weapons and fighters.
The Syrian opposition said Friday that rebel reinforcements had reached the area.
The fight for the town, which began nearly two weeks ago, has raised fears about the safety of thousands of civilians still trapped inside.
Abdel Rahman, whose watchdog relies of a network of activists, doctors and lawyers on the ground, said around 1,000 wounded people were trapped inside the town.
"The medical situation is very bad," he said.
The Syrian National Coalition, the key opposition umbrella group, praised the rebel forces in the town.
"The heroes of the Free Syrian Army prove every day that they are worthy of the responsibility that the people have entrusted them with," the group said.
"The people will continue their struggle to liberate their land, whatever it takes, and will force Hezbollah to withdraw its forces from all of Syria," it added.
The Lebanese Shiite group, a staunch ally of the Syrian regime, has dispatched fighters to help put down the uprising that began more than two years ago with peaceful protests against President Bashar al-Assad.
Some members of Lebanon's Sunni community have also crossed into neighbouring Syria to fight alongside the Sunni-led rebels forces, encouraged by local clerics.
Late Friday, influential Muslim cleric Yusuf al-Qaradawi urged Sunni Muslims throughout the region to follow suit and head to Syria to join the uprising.
"Every Muslim trained to fight and capable of doing that (must) make himself available" to support the Syrian rebels, the cleric said at a rally.
"Iran is pushing forward arms and men (to back the Syrian regime), so why do we stand idle?" added Qaradawi, a controversial figure who has millions of supporters, mostly from the Muslim Brotherhood.
Despite an official policy of neutrality on the Syrian conflict, Lebanon has found itself increasingly embroiled in its neighbour's civil war.
On Saturday morning, at least six rockets fired from Syria landed in Lebanon's eastern Bekaa region, causing no injuries.
Lebanon's National News Agency meanwhile reported that unidentified gunmen opened fire overnight at a Shiite shrine in Baalbek, a Hezbollah stronghold also in the Bekaa region.
The continued fighting has raised concerns about the prospects for a peace conference expected to convene in Geneva this month to seek a political solution to the conflict.
The Coalition reiterated on Saturday that "the immediate halt of military operations by regime forces, Hezbollah and Iran are the primary conditions for participation in the conference."
At least 114 people were killed throughout violence in Syria on Friday, including 45 rebels, 40 civilians and 29 government troops, the Observatory said.