Syrian government troops entered the center of the rebel stronghold of Qusayr Sunday, seizing the town’s main square and city hall, the military said.

“The Syrian army controls Qusayr’s main square in the center of the city, and the surrounding buildings, including the municipality building,” an army source told AFP.

State TV said 70 "terrorists" were killed while opposition activists said 30 people died, including many rebels, the BBC reported.

Rebel activists in Qusayr told Al Jazeera of "a rain of shells on the city, at the same time as artillery fire and mortar fire from dawn. Homes were destroyed and burnt down."

Qusayr, with about 20,000 residents, has been besieged for weeks by government troops. Opposition activists say members of the Lebanese militant Hezbollah group are fighting alongside President Bashar al-Assad’s troops in the area. Lebanese Sunni militia were reported fighting on the rebel side.

Earlier, Rami Abdel Rahman, of the British-based Syrian Observatory for Human Rights, told the BBC Assad’s troops were advancing from the south and Hezbollah fighters were "playing a central role."

Hezbollah denies taking part in Syria’s two-year conflict – which has killed at least 80,000 people, according to the U.N. However, the group – an ally of the Syrian regime – has held regular funerals of fighters it says were killed serving their “jihadi duties.”

In early May, the rebel Free Syrian Army told Al Arabiya that Hezbollah was using artillery shells containing fatal mustard gas in the area.

Qusayr is strategically important because it links Damascus with the coast, where Alawite regime loyalists are concentrated. It also gives rebels access to their Sunni allies in Lebanon.

Meanwhile, the Lebanese National News Agency reported that eight Soviet-made Grad rockets had struck hit the northeastern town of Hermel, across the border from Qusayr.

The agency said the short-range missiles were presumably fired from Syria but had caused no damage or casualties. Reuters said Hermel is a Hezbollah stronghold and was probably shelled by Syrian rebels.

In another sign of possible spillover into Lebanon, clashes between Sunnis and Alawites killed at least two people and wounded six others in the northern city of Tripoli Sunday, AFP reported.

Israeli Prime Minister Benjamin Netanyahu said Sunday he is "preparing for every scenario" in Syria and held out the threat of more Israeli strikes inside Syria to stop Hezbollah and other enemies getting advanced weapons.

"We will act to ensure the security interest of Israel's citizens in the future as well," Netanyahu said. Israel has neither confirmed nor denied reports that it attacked Iranian-supplied missiles stored near Damascus this month that it believed were awaiting delivery to Hezbollah. 

The Qusayr assault came as Assad vowed to continue his "fight against terrorism."

In his first interview since the U.S. and Russia announced plans for a peace conference, Assad told an Argentine newspaper that the meeting should focus on stopping the flow of money and weapons to "terrorists."