He compared the atmosphere in Lebanon now to the days before the 2005 assassination of his father, former Prime Minister Rafik Hariri, saying he believed his own life was in danger.
CGTN's Yasser Hakim confirms Saudi intelligence convinced Hariri that his life could be in peril if he traveled back to Lebanon.
"The resigning Lebanese prime minister's repetition of the unrealistic and unfounded accusations of the Zionists, Saudis and Americans against Iran is an indication that this resignation is a new scenario for creating tension in Lebanon and the region", Iranian foreign ministry spokesman Bahram Qassemi said in a statement published on the ministry website.
The country is sharply divided along a camp loyal to Saudi Arabia, headed by the Sunni Muslim Hariri, and a camp loyal to Iran represented by Hezbollah.
The 47-year-old Sunni politician's resignation comes less than a year after his government, to which Hezbollah's political wing belongs, was formed.
The Lebanese government includes Hezbollah members, and Hariri's decision aims to weaken the group's legitimate representation in domestic politics, said Sami Nader, head of the Beirut-based Levant Institute for Strategic Affairs. Lebanese President Michel Aoun, who was elected in October 2016 after more than two years of presidential vacuum, is a close ally of Hezbollah.
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Saudi Arabia and Iran are regional arch foes. "I thank all those who worked with me and placed their trust in me", Hariri added.
"I announce my resignation from the post of prime minister", Hariri said in a speech broadcast from Saudi Arabia by the Al-Arabiya news network.
Hariri was also locked in a standoff with Hezbollah over funding for the Special Tribunal for Lebanon, which is prosecuting his father's murder and had implicated Hezbollah members.
It was not immediately clear whether Hariri meant to return to Lebanon.
An official at the US State Department said it was following the situation closely and noted that Hariri had been a "strong partner in building strong national state institutions and in the war on terror". "This confrontation (between Saudi Arabia and Iran) is more violent than Lebanon can stand up to", he said, warning of economic and security ramifications.
In tweets after meeting Hariri, al-Sabhan criticized the Lebanese government for tolerating Hezbollah's criticism of the kingdom.
The Shia group and its patron Iran were the focus of Hariri's resignation speech on Saturday, which was made in Saudi Arabia, where he holds citizenship.