Lebanon PM Hariri announces surprise resignation from Saudi Arabia
Hariri, whose father Rafic was assassinated in Beirut in 2005, also cited fears over his life.
In a televised address on Saturday, he slammed Iran and the Lebanese Hizballah group for meddling in Arab affairs and said "Iran's arms in the region will be cut off".
"I announce my resignation from the post of prime minister," he said in a speech broadcast from Saudi Arabia by the Al-Arabiya news network.
The announcement came during his second visit to the kingdom in a week.
On Thursday, Hariri told the Lebanese cabinet that "Saudi Arabia is very keen on stability in Lebanon".
In a separate trip to the kingdom earlier this week, Hariri met with Saudi Crown Prince Mohammed bin Salman.
"Whenever I meet His Highness Crown Prince Mohammed bin Salman I become more convinced that we and the Saudi leadership are in full agreement on Lebanon's stability and Arab identity," said Hariri tweeted following the meeting on Monday.
Hariri was appointed prime minister in late 2016 and headed a 30-member national unity cabinet that included members of the political wing of Hizballah.
Lebanon's government has largely succeeded in protecting the country from the effects of the civil war in neighbouring Syria.
Hariri's resignation on Saturday is expected to raise tensions in the country.