Nurul Izzah Anwar said her father chose to move beyond the personal suffering he had to endure under Dr Mahathir Mohamad when he shook hands with the former prime minister.

In an interview with Australia-based programme ABC's News 24, Nurul Izzah, the PKR vice-president, described the encounter between Anwar Ibrahim and Dr Mahathir as "not easy".

"The fact that my father shook his hand and managed a warm smile, symbolised the importance of moving forward to strengthen Malaysia's democracy rather than focusing on personal suffering," she was quoted as saying.

On Monday, Mahathir made a surprised appearance at the High Court in Kuala Lumpur to show support for Anwar's application to challenge the National Security Act 2016, which grants a council headed by the prime minister emergency-like powers.

It was the first meeting between the two men in 18 years after then prime minister Mahathir sacked his deputy Anwar and had him jailed for sodomy and abuse of power.

Anwar claimed both charges were politically motivated.

Anwar was freed in 2004 after the sodomy charge was overturned but he was put behind bars again in 2015 under Prime Minister Najib Abdul Razak based on a similar charge.

Mahathir had throughout the years and until recently, insisted he was right in sacking Anwar due to "moral issues".

However, Mahathir appears ready to reconcile with Anwar now amid his attempts to unite the opposition against BN under Najib in the 14th general election.

Mahathir, who led Umno as president for 22 years, had quit the party, and together with his loyalists, formed Parti Pribumi Bersatu Malaysia (Bersatu), a splinter Umno party.

The party was set up after Najib proved impossible to dislodge from within Umno.

The former prime minister had accused Najib of corruption and demanded that he resign but Umno grassroots have thus far stood behind the latter.