Congratulatory messages are flooding social media after PKR president Anwar Ibrahim was announced as the country's 10th prime minister.

Anwar's wife Dr Wan Azizah Wan Ismail posted a simple poster of Anwar, with the text proclaiming him as the 10th PM, with the caption “Alhamdulillah”.

DAP chairperson Lim Guan Eng took to Twitter to relay his message. He wrote in Malay: "Congratulations to the prime minister chosen by Malaysians, Anwar Ibrahim. For a better Malaysia (Proud of you my PM @anwaribrahim).

Amanah strategy director Dzulkefly Ahmad tweeted that Anwar's appointment has opened up a "new chapter for Malaysia and its people".

Also on Twitter, Muda president cum Muar MP-elect Syed Saddiq Syed Abdul Rahman wrote: "Congratulations Sir, together we will make Malaysia a better place," as a caption to a photograph of him with Anwar.

Anwar also made global headlines with the announcement, with BBC writing "Anwar Ibrahim named Malaysian PM after post-election crisis."

The Washington Post reported: "Anwar named Malaysian leader, in comeback for anti-graft reformer after prison."

Anwar's appointment comes after days of negotiations and political uncertainty after last Saturday's 15th general election (GE15).

Earlier today, the Yang di-Pertuan decided to appoint the Tambun MP-elect as the PM after meeting with the Conference of Rulers.

Anwar is expected to be sworn in as prime minister at 5pm today and will lead a unity government with BN as Harapan’s main partner.