Lebanon's Prime Minister Saad Hariri announced he is resigning in a televised speech on Saturday, criticising Iran and its Lebanese ally, the Hezbollah movement.
According to Aljazeera, Hariri also said he suspected there were covert plans to target his life, but he did not elaborate.
Hariri, who made the statement during a visit to Saudi Arabia, claimed Iran planted "disorder and destruction" in the country and meddled in the internal issues of Lebanon as well as other Arab countries.
Referring to Hezbollah, Hariri claimed "Iran's arm ... has managed to impose a fait accompli on Lebanon through the power of its weapons" in the last few decades.
"They have built a state within a state," said Hariri from the Saudi capital, Riyadh.
"I say to Iran and its allies - you have lost in your efforts to meddle in the affairs of the Arab world," he continued, adding that the region "will rise again and the hands that you have wickedly extended into it will be cut off."
The leading Sunni politician has been in office for less than a year, but previously served as prime minister between 2009 and 2011.
He assumed office as prime minister again in December 2016 in a power-sharing government headed by President Michel Aoun, a supporter of Hezbollah, whose members have been charged by the International Court of Justice with assassinating Hariri's father, Rafik, in a 2005 bombing.
The country spent two years in political deadlock without a president before Aoun's election in October 2016, after Hariri endorsed the latter, a move seen by some analysts as a sign of Iran's influence in Lebanon.
His resignation now casts doubt on Lebanon's political future.
Imad Harb, a political analyst at the Arab Center in Washington DC, said for Hariri to make the announcement in Riyadh "basically it means he can’t have control over his government or his country".