A leaked flight manifesto showed Mr Najib and his wife Rosmah Mansor were due to leave on a private jet on Saturday to Jakarta, fuelling rumours he was fleeing the country to escape possible prosecution over a massive corruption scandal involving the state investment fund 1MDB.
Saudi Arabian ruler, King Fahd, assumed the office of Prime Minister on 13 June 1982 on the death of his brother, King Khalid.
The three new ministers, all leaders of the component parties of the Pakatan Harapan (PH) coalition, are finance minister Lim Guan Eng, defense minister Mohamad Sabu and minister of home affairs Muhyiddin Yassin. Lim is the chief minister of Penang state, but is largely unknown in worldwide financial circles.
Mahathir made the announcement at a press conference after a meeting attended by key PH leaders.
Council of Elders is a special team comprising of people from distinguished fields to advise the government on economic and financial matters for the next 100 days.
Mahathir, that had been sworn in as prime minister on Thursday, has pledged to investigate a multi-billion-dollar graft scandal at state fund 1Malaysia advancement Berhad (1MDB), which had been based by Najib. "The moment I got up, as I was having breakfast, I called all the officers concerned and told them all things we have to do".
He began a five-year sentence for sodomy in 2015, a charge he and his supporters say was a politically motivated move by Najib.
In Syria killed more than two dozen foreign fighters
The IAEA said meanwhile that its chief inspector Tero Varjoranta resigned, without giving a reason for his sudden departure. He said "six Syrian soldiers and 21 foreign fighters, including 11 Iranians" were among the dead.
If Mahathir will keep his word, he will work for Anwar Ibrahim to be given full pardon so he can someday still become prime minister.
Najib responded swiftly, saying he respects the immigration department's ruling and will remain in the country with his family.
On Saturday, Mr Najib, 64, said he was stepping down as chairman of the National Front coalition and president of the United Malays National Organisation - a party which dominates the group.
What followed was a major investigation by the Wall Street Journal, which reported it had seen a paper trail that allegedly traced close to $700 million from the fund to Najib's personal bank accounts.
Najib denies any wrongdoing.
Najib has been battered by a massive financial scandal, in which he was accused of overseeing the plunder of billions of USA dollars from sovereign wealth fund 1MDB.
Filings by the U.S. Justice Department in a civil lawsuit indicated almost $30 million of the money stolen was used to buy jewelry for Rosmah, including a rare 22-carat pink diamond set in a necklace.