Dubai, March 2 -- A joint military strike by the United States and Israel on Iran, which started on Saturday morning, triggered a sharp escalation across the Middle East, setting off waves of missile exchanges, mounting casualties, and far-reaching political and security repercussions.

Below is a timeline of how events unfolded:

-- Feb. 28, around 0620 GMT: Xinhua reporters in Tehran reported hearing explosions in the Iranian capital.

-- Feb. 28, around 0630 GMT: Israel's Defense Minister Israel Katz confirmed a "preemptive" strike on Iran and declared a nationwide state of emergency. Air raid sirens sounded across Israel, with emergency alerts sent to civilians.

Iran's Fars news agency reported multiple missile strikes in central Teh...