A former Iranian military official is threatening that Iran will strike Israel if the U.S. attacks Iran. 

U.S. President Donald Trump tweeted the United States will "quickly & fully" strike back if Iran retaliates. 

The former Iranian Revolutionary Guard Corps leader warned the Israeli city of Haifa and Tel Aviv could be targeted should the U.S. attack Iran. 

"This great crime will cause more dishonor for Mr. Trump, and the great nation of Iran will take a harsh revenge on the government of the U.S.," said Mohsen Rezaei. 

As the two countries escalate their threats against each other, several rockets fell in Baghdad on Sunday, including three inside the capital's heavily fortified Green Zone housing government buildings and foreign missions, the Iraqi military said.

The U.S. embassy in Saudi Arabia warned Americans "of the heightened risk of missile and drone attacks.” 

In Lebanon, the leader of the Iranian-backed militant group Hezbollah said the assassination of top Iranian commander Qasem Soleimani last week made U.S. military bases, warships and service members across the region fair game for attacks.