Prime Minister Najib Abdul Razak was about to leave his home for a much-anticipated public dialogue today when police ordered him to stay put.

This was revealed by organisers of the dialogue between the premier and NGOs, titled "Nothing to hide" at PWTC in Kuala Lumpur scheduled for this morning.

"The PM was about to leave his house... The police took over the event after informing us (of the cancellation). The police took over," said chief organiser Khairul Anwar Rahmat.

Khairul was perhaps assuring the press that Najib had no intentions of skipping the event.

The event was called off after the police claimed there were security concerns, given that two VIPs - Najib and Dr Mahathir Mohamad - were at the venue.

Khairul said the police's concerns were justified because of several scuffles that took place outside the venue resulting in arrests.

He added that when Mahathir entered the Dewan Tun Hussein Hall, there was more commotion.

"We informed everyone, including Mahathir's people, that the police advised us to postpone the event.

"We regret that his dialogue... was marred with disturbances," he said.

He said the organisers tried to encourage a culture of healthy discussions and to allow the public to pose questions to their leaders.

Khairul said he would call Najib to fix a new date for the event.

Mahathir was in the VIP holding room since 8.50am. He entered the hall after it was confirmed that Najib would not be coming.

He was greeted like a hero by the crowd, who were initially agitated with the premier's absence, and invited to speak on stage.

However, his speech was cut short by the police.

Khairul said he was unsure who invited Mahathir on stage as it was never part of the plan.