BEIRUT (AP) -- The leader of Lebanon's Hezbollah militant group vowed to help propel President Bashar Assad to victory in Syria's bloody civil war, warning that the fall of the Damascus regime would give rise to extremists and plunge the Middle East into a "dark period."
In a televised address, Sheikh Hassan Nasrallah also said Hezbollah members are fighting in Syria against Islamic radicals who pose a danger to Lebanon, and pledged that his group will not allow Syrian militants to control areas along the Lebanese border. He pledged that Hezbollah will turn the tide of the conflict in Assad's favor, and stay as long as necessary to do so.
"We will continue this road until the end, we will take the responsibility and we will make all the sacrifices," he said. "We will be victorious."
The Hezbollah leader's comments offered the clearest public confirmation yet that the Iranian-backed group is directly involved in Syria's war. They also were Nasrallah's first remarks since Hezbollah fighters have pushed to the front lines of the battle for the strategic Syrian town of Qusair near the Lebanese frontier.
The fighting in Qusair, which government troops backed by Hezbollah pounded with artillery on Saturday, has laid bare the Lebanese Shiite group's growing role in the Syrian conflict. Hezbollah initially tried to play down its involvement, but could no longer do so after dozens of its fighters were killed in the town and buried in large funerals in Lebanon.
Nasrallah, who was speaking on the anniversary of Israel's withdrawal from southern Lebanon in May 2000, used his speech in part to brace the community for the possibility of more of its men returning home in coffins.
The fight in Qusair has proven a deadly grind for both sides. On Saturday, government forces backed by Hezbollah militants shelled the town in the heaviest barrage yet of a week-long assault to dislodge rebels from the opposition stronghold, activists said.
Since the regime offensive began Wednesday, Syrian state media has said government forces have steadily gained ground. Local activists deny that pro-Assad forces have made headway and say rebel fighters are defending their positions.
The Britain-based Syrian Observatory for Human Rights said at least 30 people, including 27 rebels, were killed and dozens wounded Saturday in the town, which holds strategic importance for both the regime and the opposition.
For Assad, Qusair's value lies in its location along a land corridor linking two of his strongholds, the capital of Damascus and towns on the Mediterranean coast, the heartland of his minority Alawite sect, an offshoot of Shiite Islam. For the rebels, holding Qusair means protecting a supply line to Lebanon, 10 kilometers (six miles) away.
Saturday's barrage of rockets, mortar rounds and tank shells began after daybreak, said Qusair activist Hadi Abdullah and the pro-opposition Observatory. Both said it was the most intense shelling since the regime launched its offensive there a week ago.
Hezbollah has come under harsh criticism at home and abroad for sending its gunmen to Qusair, and Nasrallah's gamble in Syria primarily stems from his group's vested interest in the Assad regime's survival. The Syrian government has been one of Hezbollah's strongest backers for decades and the militant group fears that if the regime falls it will be replaced by a U.S.-backed government that will be hostile to Hezbollah.
Nasrallah on Saturday defended his group's deepening involvement and sought to frame the fight next door as part of a broader battle against Israel.
"Syria is the back of the resistance, and the resistance cannot stand, arms folded while its back is broken," Nasrallah told thousands of supporters from a secret location via a video link.
"If Syria falls into the hand of America, Israel and takfiris, the resistance (Hezbollah) will be besieged and Israel will enter Lebanon and impose its will," Nasrallah said. Takfiri Islamists refers to an ideology that urges Sunni Muslims to kill anyone they consider an infidel.
Syria's fall, he said, would mean "Palestine will be lost" and "the people of our region and its nations will enter a bad and dark period."
Along with Iran, Syria has been the main backer of Hezbollah. Much of the group's arsenal, including tens of thousands of rockets, is believed to have come from Iran via Syria or from Syria itself.
Hezbollah's role has drawn intense criticism from Syria's main opposition group.
"Some Lebanese are being sent to Syria as invaders in order to return back home in coffins draped with shame," said George Sabra, the acting head of the Syrian National Coalition.