As Iran retaliates, largest US military base in Middle East hit by ballistic missile, Qatar says

In a statement on Monday, amid ongoing strikes against Lebanon, the Israel Defense Forces said, "The strikes continue — their intensity will increase.”

Overnight, the IDF had launched a series of strikes in Beirut and Southern Lebanon. The IDF said senior Hezbollah members were targeted in the Beirut area among the strikes.

Earlier on Monday, Lebanon had launched projectiles toward northern Israel that were intercepted.

"Shortly after Hezbollah’s rocket fire, in accordance with planning, we launched a first broad wave of strikes in Beirut and southern Lebanon, targeting senior operatives, headquarters, and terrorist infrastructure. We are also acting to evacuate civilians in southern Lebanon ahead of further strikes," the IDF said.

Secretary of the Supreme National Security Council of Iran, Ali Larijani, released a statement on X on Monday, saying, "We will not negotiate with the United States."

Larijani's statement was in response to a report about a possible resumption of talks with the U.S. in the wake of the operation in Iran over the weekend.

In another post, Larijani mentioned the American casualties in the operation, which left three U.S. service members killed and five wounded.

"Trump plunged the region into chaos with his 'delusional fantasies' and now fears more American troop casualties," Larijani said.

"Today, the Iranian nation is defending itself. The armed forces of Iran did not initiate the aggression," he added.

The Department of Homeland Security has warned of potential lone-wolf and cyberattacks amid the ongoing strikes in Iran, according to a law enforcement bulletin obtained by ABC News.

"Although a large-scale physical attack is unlikely, Iran and its proxies probably pose a persistent threat of targeted attacks in the Homeland, and will almost certainly escalate retaliatory actions—or calls to action—if reports of the Ayatollah’s death are confirmed," according to the bulletin.

"In the short-term, we are most concerned that Iran-aligned hacktivists will conduct low-level cyber attacks against US networks, such as website defacements and distributed denial-of-service attacks,” officials said in the bulletin.

The alert was issued on Saturday, a day before a gunman opened fire in Austin, Texas, and authorities are investigating whether or not the suspect was inspired by the situation overseas.

Law enforcement sources told ABC News the suspect was wearing a sweatshirt with “Property of Allah” on it and underneath, a shirt with “Iran” and the Iranian flag on it.

-ABC News' Luke Barr

Bahrain's Interior Ministry released a statement saying one person was killed and two others were injured after a fire broke out on a foreign ship in Salman Industrial City, as a result of falling debris from an intercepted missile.

Officials said the fire has been brought under control and extinguished.

-ABC News' Will Gretsky