Syria's opposition National Coalition warned Tuesday that 30,000 civilians in the rebel-held town of Qusayr faced an "extremely dangerous situation" as regime troops prepare to attack.
President Bashar al-Assad has "mobilised military forces in the direction of the city of Qusayr, in the province of Homs," the statement said, describing reports of dozens of tanks and large groups of soldiers on the outskirts of the town.
"The Syrian Coalition stresses that this is an extremely dangerous situation. We warn civil society of these new crimes that Assad may soon commit against the residents of Qusayr."
The statement called on NGOs to head to Qusayr and for quick international action "to help save 30,000 civilians facing imminent danger."
"We ask the (UN) Security Council to issue a decision forcing Lebanon to control its borders, and thus guarantee the withdrawal of Hezbollah members from Syrian territory," the coalition said.
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Lebanese Shiite militant group Hezbollah, an Assad ally, has dispatched its fighters to battle alongside regime troops in the Qusayr region, near the border with Lebanon.
The regime has made recapturing the town and the area in central Homs province a key objective, and fierce fighting has raged in the vicinity for months.
In recent weeks, regime forces backed by Hezbollah and members of the National Defence Forces, a pro-regime militia, have advanced in the region, taking a string of villages and reportedly surrounding the town of Qusayr on three sides.
A military source last week said leaflets had been dropped on the town, urging civilians to leave via a safe passage, but activists in Qusayr said no leaflets were dropped and there was no safe way out.
The Syrian Observatory for Human Rights has also expressed concern about what might follow a regime advance into the town of Qusayr, a rebel bastion which has resisted the army for the past year.
The head of the Britain-based monitoring group, Rami Abdel Rahman, told AFP that he feared a "massacre" in the town.