The Israeli military issues an "urgent warning" to people in Beirut's southern suburbs and in dozens of villages, as witnesses report blasts in the capital.
US Secretary of State Marco Rubio says "the hardest hits" on Iran are "yet to come", adding he would not "give away details of our tactical efforts".
The US embassy in Riyadh has been hit by two drones, resulting in a "limited fire and minor material damage to the building", according to the Saudi defence ministry.
It follows Donald Trump saying he took the decision to launch a war against the country because it was the "last, best chance" to stop its regime.
The US and Israel struck Iran on Saturday, killing Supreme Leader Ayatollah Ali Khamenei. The Israeli military has since launched new strikes on Tehran.
Israel has also launched multiple strikes on what it said were Hezbollah targets in Lebanon, warning that military operations won't end until the threat is fully "removed".
Lebanon's health officials say Israeli strikes have killed 52 people as hundreds of Beirut residents have been forced to evacuate to shelters as a result of the bombing.
