The US launched strikes on Iran late Tuesday for the 11th consecutive night, as Tehran warned Washington not to target its nuclear facilities.
US Central Command (Centcom) said the wave of attacks was "designed to further degrade Iran's ability to threaten commercial shipping" in the Strait of Hormuz.
Iranian state media reported that air defenses were activated in the capital Tehran. Explosions were also reported in Tabriz, Chabahar, Konarak and Bushehr, home to Iran's only nuclear power plant.
Iran, which has been retaliating against the US and its allies in the Middle East, has warned of retaliation after US President Donald Trump said the US would soon strike an underground nuclear facility near Natanz.
Iran and the US agreed to a ceasefire in April, but hostilities resumed last week as the two countries clashed over control of the vital Strait of Hormuz waterway.
Centcom announced that US forces had struck Iranian military operations centers, naval facilities, aircraft hangars, drone depots and military logistics infrastructure.
It has also accused Iran of attacking more than 30 commercial ships passing through the Strait of Hormuz over the past three months.
"These unjustified attacks have endangered hundreds of innocent sailors and undermined freedom of navigation," it said in a statement, adding that the waterway remains open to the passage of commercial ships.
Kuwait's military announced Wednesday morning that its air defense systems were facing drone attacks from Iran, while Bahrain and Jordan said they had also thwarted drone and missile attacks.
Earlier, Trump said the next military target could be a complex known as Pickaxe Mountain, an underground nuclear facility where Iran is suspected of building an undeclared uranium enrichment plant.
"We will strike that area very quickly and with great force," Trump said during a statement to reporters at the White House, in a meeting with Lebanese President Joseph Aoun.
He added that he would not normally announce military targets in advance, but "there is nothing they can do to prevent it."
Trump has also threatened to "deal" with the Houthi rebels if the Iran-backed militant group in Yemen carries out its threat to block Saudi ports.
Earlier, a Houthi media official had stated that they were closing the Bab al-Mandab Strait, the southern entrance to the Red Sea, to Saudi ships.
The Red Sea has become a vital route for transporting oil from Saudi Arabia during the US-Israeli war against Iran, which has led to the de facto closure of the Strait of Hormuz.
Rubio warns of 'dangerous precedent' if Iran is allowed to control Hormuz
US Secretary of State Marco Rubio said Iran "is not serious about talks" during his opening remarks at the Association of Southeast Asian Nations (ASEAN) foreign ministers' meeting held in Manila, Philippines, on Wednesday.
"The United States is always committed to diplomacy. We are open and always ready to engage, negotiate and resolve disputes," Rubio declared.
He added that "the problem we currently have (with Iran) is that they are not serious about talks.
"If they are serious, so are we. If not, then we will do what is necessary to protect our interests, as well as the interests of our allies."
Rubio has warned of setting a "dangerous precedent" if Iran were allowed to control the Strait of Hormuz, saying they "do not have, under any existing legal mechanism," the right to control the movement of traffic through this international waterway.
"The fundamental principle of freedom of navigation is at stake," Rubio declared.
"If this principle is threatened, then I think the global economy is also threatened, as well as the rules that have supported 150 years of international trade," he declared.
The Strait of Hormuz was fully open for free and safe passage before the US and Israel attacked Iran in February, at the start of the conflict.
Iran sees control of this waterway as its most valuable tool of pressure in negotiations and, in recent weeks, has repeatedly fired on ships that it says had not communicated with Iranian authorities before passing through.