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 that extremists’ 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.