BEIRUT, Lebanon — The leader of Hezbollah declared on Friday that extremists claiming to act in the name of Islam did more harm to the religion than any cartoon.

Hassan Nasrallah, Hezbollah’s chief, said in a televised address thatextremists’ beheadings and massacres hurt the Prophet Muhammad more than mocking him in books, films or drawings.

Though he did not specifically mention Wednesday’s killings of 12 people at a satirical newspaper in Paris by Islamist militants, Mr. Nasrallah was clearly referring to those events, as well as the rise of Sunni extremist groups like Al Qaeda and the Islamic State. He said such extremists posed “the biggest threat to Islam” today, one that “has never happened before in history,” and called on “all Islamic sects” to confront them, “work to isolate them, surround them and end it.”

Some social media users reacted with surprise in the West, where Hezbollah, the Shiite militant group that is also Lebanon’s strongest political party, is known for taking Americans captive in the 1980s, and for its alliance with Iran, whose leader in 1989 called for the death of Salman Rushdie over his novel “The Satanic Verses.” But the statement fit with Mr. Nasrallah’s remarks in recent years. He has spoken more and more of the threat from Al Qaeda and the Islamic State, calling them a danger not only to Shiites but also to people of all religions across Lebanon, the region and the world.

Without abandoning its original mission of fighting Israel, Hezbollah has increasingly focused on the Islamic State and the Qaeda-affiliated Nusra Front, which have gained power in neighboring Syria during its civil war. Hezbollah has cited them as a reason for its intervention there to prevent the overthrow of President Bashar al-Assad.

Hezbollah and Iran have sought to recast themselves as posing little threat to the West compared with those Sunni jihadist organizations — and even as potential allies against them. The Paris attacks provided another moment to drive home the point.

Mr. Nasrallah calls those groups takfiris — a term for Muslims who declare other Muslims apostates deserving of death. The Sunni militants of Al Qaeda and the Islamic State view Shiites as apostates, and Hezbollah’s Shiite base increasingly views them as an existential threat.

Critics of Hezbollah and Iran say that as allies of Mr. Assad’s, they bear some responsibility for the rise of extremists in Syria, citing Mr. Assad’s crackdown on protesters, along with the lack of international support for relatively moderate insurgents. And they note that Hezbollah needs Mr. Assad in power to facilitate the flow of arms from Iran.

Hezbollah’s tone was not always this way. In 2006, when some Muslims rioted over a Danish newspaper’s cartoons satirizing the Prophet Muhammad, Mr. Nasrallah declared that the insult would not have happened if someone had carried out the Iranian fatwa against “the renegade” Mr. Rushdie. “I am sure there are millions of Muslims who are ready to give their lives to defend our prophet’s honor,” he said then.

And in 2012, Hezbollah tangled with a Lebanese artist who depicted Mr. Nasrallah, even though the likeness was rather flattering.