Lebanese Prime Minister Saad al-Hariri has resigned, saying in a televised broadcast from Saudi Arabia that he feared for his life, while also fiercely criticising Iran.
He accused Iran of sowing "fear and destruction" in several countries, including Lebanon.
Mr Hariri's father, former prime minister Rafik al-Hariri, was assassinated in 2005.
The Hariri family is close to Saudi Arabia, Iran's regional competitor.
Mr Hariri has been prime minister since December 2016, after previously holding the position between 2009 and 2011.
"We are living in a climate similar to the atmosphere that prevailed before the assassination of martyr Rafik al-Hariri," he said in the broadcast from the Saudi capital Riyadh.
"I have sensed what is being plotted covertly to target my life."
Mr Hariri also attacked the Iran-backed Shia movement Hezbollah, which wields considerable power in Lebanon.
Addressing "Iran and its followers" he said Lebanon would "cut off the hands that wickedly extend into it".
Iran said the resignation would create regional tensions and rejected Mr Hariri's accusations as "unfounded".