Dr Mahathir Mohamad has claimed that Prime Minister Najib Abdul Razak is under the spell of one "RM", without mentioning the person's name.

"Najib is not only under the spell of RM, but RM has many shamans from all over the world who promise that Najib won't fall (from power)," he said.

The former premier said this in response to a question on whether Najib was under the influence of black magic during a dialogue session in Pasir Gudang, Johor this afternoon.

Mahathir said regardless of "RM's" spells, the prime minister's position will not be immune to people's power.

"But InsyaAllah (God willing), if the people show people's power, he won't stay (as prime minister)," he said.

Earlier, his arrival at the event titled "Malaysia hari ini: Ke mana kita" (Malaysia today: Where are we heading) was met with a rousing applause and cheers of "Hidup Tun".

At about 7.30pm, Mahathir and his wife Dr Siti Hasmah Ali made a surprise visit to Dataran Merdeka where thousands of Bersih 4 protesters were gathered.

Among others, Bersih 4 is demanding for Najib's resignation.

Mahathir too has repeatedly called on the prime minister to step down and accused him of numerous misdeeds.