Washington/Jerusalem - The United States and Israel on Saturday launched "major combat operations" against Iran after the recent U.S.-Iran nuclear talks in Geneva failed to yield a deal to avert the crisis.

U.S. President Donald Trump said on Saturday that the United States had begun "major combat operations" in Iran.

"Our objective is to defend the American people by eliminating imminent threats" from Iran, Trump said in a video shared on social media.

Iran can never have a nuclear weapon and the United States plans to destroy Iran's missiles and raze its missile industry to the ground, said Trump.

Earlier on Saturday, the Israeli Defense Ministry said in a statement that the country launched a "preemptive" strike against Iran "to remove threats to Israel."

Apparent strikes in Tehran happened near the offices of Supreme Leader Ayatollah Ali Khamenei, according to media reports. Multiple missiles also hit University Street, Jomhouri area and elsewhere in Tehran. Explosions were also heard in Iranian cities, including Isfahan, Qom, Karaj, Kermanshah and Ilam.

Iran closed its airspace while the attack was ongoing. Mobile phone services have been cut in parts of Tehran.

Meanwhile, Israel's Defense Minister Israel Katz declared a special and immediate state of emergency in all areas of Israel. Sirens were sounded across Israel to warn the public to prepare for the possibility of Iranian retaliation. Israeli airspace has been closed to civilian flights, according to Israeli Airports Authority.

The Israeli Defense Ministry warned that a missile and drone attack against Israel and its civilian population is expected in the immediate future.

The Israel Defense Forces has prohibited educational activities, public gatherings, and attendance at workplaces, allowing exceptions for essential services.

Takeoffs and landings at Ben Gurion International Airport near Tel Aviv have been halted, and passengers were advised not to come to the airport, according to the airport's authority.

The attacks against Iran came after the U.S.-Iran nuclear talks concluded in Geneva on Thursday. Tensions between the United States and Iran were soaring amid massive U.S. military buildup in the Middle East and the stalled nuclear talks.