"US forces began launching strikes against Iran at 8:00 p.m. ET today (0000 GMT)," US Central Command said in a statement.
"The strikes are a powerful response to yesterday's attempted Iranian attacks on US forces based in the Middle East."
Earlier on Wednesday, a drone hit a US-owned gas storage tanker at Egypt's Mediterranean port of Damietta, British maritime security firm Ambrey said in an initial assessment, while US and Saudi forces launched strikes against Iran-aligned groups in eastern Iraq and Iran fired missiles at U.S. troops in Jordan.
A statement from Egypt's petroleum ministry confirmed a fire at the port but made no mention of a drone attack. It was not immediately clear who was responsible.
The latest strikes in Iraq and Egypt threatened to draw more Middle Eastern countries into the conflict, after the Iran-aligned Houthis in Yemen last week declared a naval blockade on Saudi Arabia.
The US strikes in Iran on Wednesday followed President Donald Trump's vow earlier in the day to retaliate against Iran for firing on US troops.
"So it's our turn," Trump told reporters at the White House, promising to "hit them very hard" even as he again said Washington would continue to aim for a peace deal with Tehran.
