Mr. Nasrallah called the resignation “very destabilizing” and rejected Mr. Hariri’s accusations of Iranian interference in Lebanon. He also pointed out the irony of his making them from Saudi Arabia, and said, “We, Hezbollah, did not wish for this.”
But he urged people not to engage in street protests or “sectarian tensions,” and “not to fear and worry,” adding, “Civil peace in Lebanon is the most precious.”
Mr. Nasrallah said he expected Mr. Hariri to return to Lebanon on Thursday — “if he is allowed to come back” — and talk with President Michel Aoun, a Hezbollah ally, who has yet to accept the resignation.
“It was definitely a Saudi decision that was imposed on him,” said Mr. Nasrallah. “It was not his will to step down.”
A satirical website, “Free Saad Hariri,” has already appeared, with a time counter showing how long it had been since he resigned. It was reminiscent of a billboard Mr. Hariri maintains in Beirut to count the days waiting for justice after the 2005 assassination of his father, Rafik Hariri, a former prime minister.
Sami Nader, an economist at St. Joseph University in Beirut, said Mr. Nasrallah appeared to be “trying to de-escalate the situation and contain it” because the resignation, which leaves Hezbollah without a Sunni governing partner, could strip it of “legal and political cover.”
It could also make the Lebanese government more vulnerable to sanctions against the group, which is listed as a terrorist organization by the United States.
Mr. Nasrallah also sought to tamp down fears that the prime minister’s resignation exposed Lebanon to a new war with Israel, where high-ranking officials have lately argued that Hezbollah and the Lebanese government are one and the same. If Israel wanted to wage a war, he said, it would do so regardless of whether Mr. Hariri was in government or not.
Mr. Hariri had warned of a plot against his life, and Saudi news outlets said one had been foiled last week. But the Lebanese Army and internal security forces said they knew of no such attempt.
The unity government was meant to contain rifts in Lebanon exacerbated by the war in Syria, where Iran and Saudi Arabia and their respective Lebanese partners have supported opposite sides. It has produced some results after years of political deadlock: a new electoral law, budget talks, a tax law and even a decision on the contentious issue of appointing an ambassador to Damascus.
But while Mr. Hariri has made many concessions to Hezbollah — tolerating its growing involvement in Syria and its adoption of state functions like negotiating hostage releases and fighting militants on the borders — Hezbollah has not made as many concessions to him, angering his base. That meant Mr. Hariri could have faced challenges in elections planned for May.
Now, it remains unclear if those elections will take place, or what the next steps are in the governance crisis. The two most likely Sunni politicians — under Lebanon’s sect-based power-sharing system, the prime minister must be Sunni — former prime ministers Najib Mikati and Fouad Siniora, have said they are not interested.
If Mr. Aoun and the Parliament decide on an openly pro-Hezbollah figure, the country could face new isolation. It is unlikely they could settle on an openly anti-Hezbollah political figure.
Mr. Hariri, perhaps seeking to dispel rumors he was under arrest in Saudi Arabia, posted on Twitter for the first time since his resignation speech, posing with the new Saudi ambassador to Lebanon.
Lebanese supporters and opponents of Mr. Hariri’s faction said the country would soldier on with or without him.
“Hariri? What does that have to do with us? Everyone in this area is against him anyway,” said Mohammad Shabban, the owner of a shawarma shop. “Saudi tells him what to do. They say go-go, he goes-goes; they say come come, he comes.”