Former opposition leader Anwar Ibrahim believes Dr Mahathir Mohamad's presence in court today showed the former premier's support for the reform agenda.

This will provide them a platform to continue to engage, he said when met at the High Court in Kuala Lumpur after his application to challenge the National Security Council Act 2016 (NSC Act).

The jailed PKR de facto leader was asked whether he trusted Mahathir after what he wrote to PKR leaders and members in a letter, cautioning them against any cooperation with his long-time nemesis.

Reporter: Do you trust Mahathir?
Anwar: I express my appreciation... the fact that he was kind enough, and his support for the application. (He) wished me success and well.

Reporter: Do you trust him now?
Anwar: No, we will continue to engage...

Reporter: You trust him now as compared (to the time) you wrote a letter warning members not to trust him?
Anwar: My position is number one, the welfare of the people is paramount, which means whoever wants to engage, must accept our reform agenda. It is not about trusting or not. Anyone who supports the reform agenda must be given a chance to continue (to do so).

Reporter: Has he earned your trust?
Anwar: He has showed preparedness to come and pledge his support for the application and wish me well and I presume, therefore, he supports the reform agenda. We discussed other issues, just in general. We focused on the application but we did discuss other issues. We will announce it.

"We also discussed other issues but we will look at it and see the relevance and importance in regard to the reform agenda and the people in order to save Malaysia.

"We will announce it accordingly at a later date," he added.

Mahathir appeared for nearly an hour at the court complex and met Anwar in the courtroom.

Also present were opposition leader Dr Wan Azizah Wan Ismail, PKR vice-president Nurul Izzah Anwar and DAP vice-president Teresa Kok.

Anwar's supporters were in high spirit and chanted 'reformasi' and 'free Anwar' when the former deputy prime minister was taken out of the court.

Wan Azizah declined to reveal the discussion between Anwar and Mahathir which took place earlier at the witness room.

"He came to wish Anwar well and it was a pleasant surprise. He wished him (Anwar) good luck and we take it from there," she told reporters.