Bahrain is often seen as a bellweather for the Saudi Arabia-dominated Gulf Cooperation Council, which regularly announces sanctions and travel bans targeting countries seen as friendly with Iran.
The Bahraini order and an additional ban on travel to Lebanon marks the latest escalation in a multi-fronted confrontation between Saudi Arabia and Iran which is playing out on political and military battlefields throughout the region, including Lebanon, Syria and Yemen.
Mr Hariri delivered his resignation speech from the Saudi Arabian capital Riyadh, where he claims to have fled for his own safety, citing a foiled assassination attempt by Iran on his way out of Lebanon.
He accused Iran of meddling in Lebanese politics and taking the country “as hostage”. He said the atmosphere in Lebanon now was similar to that in 2005, when his father, former prime minister Rafik al-Hariri, was assassinated in a car bombing.
Iran’s Foreign Ministry described Mr Harisi’s resignation as a “plot jointly designed by Saudi Arabia and Israel” and denied being behind any attempt on his life.
Sayyed Hassan Nasrallah, the leader of Lebanese Shia militia Hizbollah, on Sunday accused Saudi Arabia of meddling in Lebanese affairs by orchestrating the resignation.
“The resignation was a Saudi decision dictated to prime minister Saad al-Hariri and forced on him,” Nasrallah said in a televised broadcast.
Iran and Saudi Arabia have long sparred in the Lebanese political arena. Hizbollah is allied to and backed by Tehran, and is widely seen as projecting Iranian influence.
Mr Hariri, scion of a Sunni Lebanese polity dynasty, was seen to have extended an olive branch to Hizbollah when he formed a national unity government less than a year ago.
The president of that government, Michel Aoun, who is a political ally of Hizbollah, said he would not accept Mr Hariri’s resignation until the prime minister returns to Lebanon.
While many analysts saw Mr Hariri’s resignation as evidence that Hizbollah was being pushed back, some fear it will lead to further instability in an already fragile country.
“The situation is open to all scenarios, including violence,” said Hanin Ghaddar, a Lebanon analyst with the Washington Institute.
With no “substantial” Sunni leader likely to want to take Mr Hariri’s place in a Hizbollah-dominated government, further power grabs by Iranian-backed elements are a near-certainty, she said.
“The Iranians have so many people in Lebanon, I wouldn’t be surprised if they kill again. This is their strategy. They do that, they kill people. They do not stop.”