Israel announced strikes on government infrastructure in Tehran on Monday.
President Donald Trump announced "major combat operations" against Iran on Feb. 28, with massive joint U.S.-Israel strikes targeting military and government sites, officials said.
Ayatollah Ali Khamenei was among those killed in Tehran on the first day of strikes, and his son Mojtaba Khamenei was chosen to succeed him. Iran is responding with missile and drone attacks targeting Israel, regional U.S. bases and multiple Gulf nations. Iran is also attempting to block some shipping traffic through the Strait of Hormuz.
Israel is also intensifying its long-running strike campaign against the Iran-backed Hezbollah militia in Lebanon.
The near-total internet blackout in Iran entered its 23rd day early on Sunday, according to NetBlocks, a web monitoring organization.
"The measure adds to the wartime distress of millions of civilians who lack independent sources of information and alerts," NetBlocks said.
A shell launched from Lebanon into northern Israel resulted in damage, the Israel Defense Forces said on Sunday.
"The incident is under investigation," an IDF spokesperson said. Israel has been targeting infrastructure related to Hezbollah, an Iranian proxy, in southern Lebanon.
Israel's first responders said two vehicles had caught fire near the border, adding in an update that there appeared to be someone "trapped in a vehicle, showing no signs of life."
President Donald Trump said the U.S. will "hit and obliterate" Iranian power plants if the Strait of Hormuz isn't opened within 48 hours
"If Iran doesn't FULLY OPEN, WITHOUT THREAT, the Strait of Hormuz, within 48 HOURS from this exact point in time, the United States of America will hit and obliterate their various POWER PLANTS, STARTING WITH THE BIGGEST ONE FIRST!" Trump said in a post on his social media platform.
The largest power plant in Iran is thought to be the Damavand Combined Cycle Power Plant - which is located in the outskirts of the capital city Tehran.
Iran has effectively blocked the Strait of Hormuz -- a narrow waterway off Iran's southern coast that normally handles about 20% of global oil consumption -- since the start of the war.
Trump's post came as he floated on Friday that he was considering "winding down" the U.S.'s military campaign, claiming the U.S. was "very close to meeting our objectives."
Trump also said Friday that the U.S. would "help" Gulf states secure and police the Strait of Hormuz "if asked."
Israel's MDA service said Saturday that 64 people were injured in an Iranian attack on the city of Arad in southern Israel.
Of those wounded, seven patients were in serious condition and 15 patients in moderate condition, according to MDA.
IDF Spokesperson Effie Defrin said the hits in Arad and earlier in Dimona on Saturday were direct missile strikes.
"The air defense systems were activated but did not intercept the missile. We will investigate the incident and learn from it," he said.
-ABC News' Dana Savir and Victoria Beaule
