The Syrian border town of Qusayr came under heavy shelling on Saturday as the country's army launched a three-pronged attack on the rebel-held town.
The army offensive to recapture Qusayr began last Sunday, and the rebels in the town said they are under heavy bombardment from Lebanese Hezbollah militants, who support Syria's government.
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The strategically important town between Homs and the Lebanese border was hit by two ground-to-ground missiles and an air strike, as well as artillery and rocket fire, activists said.
The Hezbollah fighters are reportedly trying to advance again in order to push rebels out.
"I've never seen a day like this since the battle started," said Malek Ammar, an activist speaking to Reuters from the town by Skype. "The shelling is so violent and heavy. It's like they're trying to destroy the city house by house."
Qusayr is important to Syrian President Bashar Assad because it sits in an area linking two of his strongholds: the capital of Damascus and towns on the Mediterranean coast. Conquering the town would effectively divide rebel-held territories in the north and south.
For rebels, holding Qusayr means protecting a supply line to Lebanon, only six miles away.
Assad's forces are thought to have seized about two-thirds of Qusayr, but rebels said they are preventing any further advances, which are said to be happening at a very slow pace.
"We are in the second phase of our plan of attack but the advance has been quite slow and difficult," a Hezbollah fighter told Reuters. "The rebels have mined everything, the streets, the houses. Even the refrigerators are mined."