Former Malaysian leader Mahathir Mohamad will be questioned over statements made at massive weekend demonstrations, held to demand current Prime Minister Najib Razak's ouster over corruption allegations.
The 90-year-old Mahathir, Malaysia's longest-serving prime minister, electrified crowds at the protests in Kuala Lumpur by calling for a sustained public push to topple Najib.
He also accused Najib of bribing politicians in the ruling UMNO party for their support, saying the prime minister was clinging to power to avoid corruption charges.
"We will call him (Mahathir). He has made speeches and accusations," national police chief Khalid Abu Bakar has been quoted saying by online news outlet Malaysiakini.
"Among them, he claimed UMNO leaders had taken bribes, so we want to find out more."
Malaysia's ruling coalition routinely hauls in opponents who take part in anti-government actions, in what the opposition calls a pattern of systematic harassment.
It was not clear whether Mahathir, who remains influential in the ruling party, would face any charges.
Organisers of the weekend demonstrations also have said they had been ordered to report to police on Wednesday.
Najib has been under pressure since The Wall Street Journal revealed that Malaysian investigators found nearly US$700 million (NZ$994.47 million) had been deposited into his personal bank accounts.
His government has since admitted the deposits occurred, calling them "political donations" from Middle Eastern sources, but have refused to give further details.
Outrage over the scandal has been heightened by Najib's subsequent actions - including sacking Malaysia's attorney general - that appear to have stalled investigations.
Najib had already been facing demands for months that he explain the whereabouts of huge sums allegedly missing from deals involving a state-owned company he launched.
He denies any wrongdoing, saying he is the victim of a "political conspiracy".