In his first address as Malaysia's seventh Prime Minister, Tun Dr Mahathir Mohamad has pledged to abolish the term "cash king" under the Pakatan Harapan-led administration.
Dressed in traditional Malay dress, Mahathir took the oath of office at a ceremony in Kuala Lumpur on Thursday.
As he was inaugurated, hundreds of revellers outside the palace cheered and sang the national anthem, with some breaking down in tears. Dr Mahathir began his with a warning to the outgoing prime minister that he now faces possible prosecution.
In a statement, the palace rejected the news claiming that King Sultan Muhammad V delayed the appointment of Mahathir.
"His Majesty strongly supports and respects the democratic process and the wishes of his subjects", the statement by Datuk Wan Ahmad Dahlan Ab Aziz, Comptroller of the Royal Household, said.
Having ruled Malaysia previously for 22 years, Mahathir certainly knows where all the policy levers are.
The election result is a political natural disaster for the Muslim-majority country, sweeping aside the 60-year rule of the National Front and its leader Najib Razak, whose reputation was tarnished by a monumental corruption scandal, a crackdown on dissent and the imposition of an unpopular sales tax that hurt many of his coalition's poor rural supporters.
The following is an explanation of how seasoned campaigner and long-time leader Mahathir Mohamad, 92, led an opposition alliance to victory over Prime Minister Najib Razak's BN.
Mahathir undoubtedly helped to carry the opposition to victory by appealing to voters sick of Najib's corruption-plagued rule, but his comeback has also been controversial.
Official results showed that Mahathir's coalition won 121 seats, comfortably more than the 112 required to rule.
In jubilant mood and cracking jokes, Mahathir dismissed any doubts he would be prime minister.
"The election commission was quite slow", he said, noting that results were announced at 4am, but the king only got the result in written form at 3pm on Thursday afternoon.
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In a report Wednesday, the London-based consultancy said Mahathir's win would have "far-reaching consequences for the economy", both negative and positive.
Malaysian markets were closed and will reopen only on Monday, but overseas investors were nervous about the ouster of Najib and the ringgit lost four percent in offshore trading.
What action is Mahathir promising?
Some economists raised concerns his populist promises could undermine economic prospects at an increasingly challenging time for emerging markets, despite hopes elsewhere he may revive his bold approach to economic management.
Fazly, a former member of the ruling party's youth branch, noted that it was good for Malaysia to experience its first transition of power.
Rising living costs also weighed heavily on many voters and saw them peel away from Mr Najib and his once unshakeable coalition. Before the poll he had promised to step aside once Anwar was free and let him become prime minister.
Anwar's wife, Wan Azizah Wan Ismail, is to be deputy prime minister.
Najib's defeat could be just the start of his problems - Mahathir has vowed to bring him to justice over allegations that billions of dollars were looted from sovereign wealth fund 1MDB, which the scandal-hit leader set up and oversaw.
On the campaign trail, Mahathir harped on the 1MDB scandal and a popular perception that Najib's family led a lavish lifestyle.
Ninety-two-year-old Mahathir Mohamad was sworn in on May 10 as the world's oldest elected leader.