Malaysian police have said they will call on former Prime Minister Mahathir Mohamad to give a statement on allegations he made against Prime Minister Najib Razak at an anti-government rally in Kuala Lumpur last weekend.

A police spokesperson said that Mahathir, Malaysia’s longest-serving prime minister had made comments that warranted action.

“We will call him [Mahathir]. He has made speeches and accusations,” national police chief Khalid Abu Bakar was quoted as saying by online news outlet Malaysiakini on Wednesday.

“Among them, he claimed UMNO [the ruling United Malays National Organisation, Malaysia’s largest political party] leaders had taken bribes, so we want to find out more.”

Mahathir, 90, electrified crowds at the demonstrations by tens of thousands in Kuala Lumpur on Sunday by calling for a sustained public push to topple Najib.

He also accused Najib of bribing UMNO politicians for their support, saying the premier was clinging to power to avoid corruption charges.

It was not clear whether Mahathir, who remains influential in the ruling party, would face any charges.

Organisers of the weekend demonstrations – the electoral reform pressure group Bersih, which means “Clean” – also have said they had been ordered to report to police on Wednesday.

Bersih’s official T-shirts and logo have been banned by police, but thousands of peaceful, yellow-clad protesters gathered near the city’s Independence Square during the two-day protest on Saturday and Sunday.

Najib has been under growing pressure since The Wall Street Journal revealed in early July that Malaysian investigators had found nearly $700m in mysterious deposits in his personal bank accounts.

Meanwhile, Bersih could expect to be slapped with a RM65,000 ($15,460) clean-up bill this week, the country’s local government minister Datuk Abdul Rahman Dahlan told local media.

The group reportedly collected RM1.5m ($356,000) in donations at the rally. Al Jazeera