Anwar said this week he has secured a "strong, formidable" majority from lawmakers in parliament to oust Prime Minister Muhyiddin Yassin. But he has to convince the king that he has the numbers to form a government.

The political turmoil comes just seven months after another power struggle that led to Muhyiddin getting the premiership and could delay efforts to stabilise an economy that is reeling from the impact of the coronavirus pandemic.

Muhyiddin, who has a razor-thin majority in parliament, has dismissed Anwar's claims of a majority and challenged him to prove it through a constitutional process.

The king plays a largely ceremonial role in Malaysia but he could appoint a prime minister who in his view is likely to command a majority in parliament. He could also dissolve parliament and trigger elections on the premier's advice.

"His Majesty has been advised by his doctors to remain at (hospital) for seven days for observation. So until then, he will not have any meetings," palace comptroller Ahmad Fadil Shamsuddin told Reuters.

Anwar was scheduled to meet with the king on Tuesday but the appointment had to be cancelled as the king was unwell and had to be taken to a hospital.

No major political party has come out in his support but the leader of the United Malays National Organisation (UMNO), the largest party in the ruling coalition, said there had been defections to Anwar's camp.

In a campaign speech in Sabah state, Prime Minister Muhyiddin again questioned Anwar's claim that he has a majority, state news agency Bernama reported.

"He made a statement and when asked on the number supporting him and who have given their statutory declaration of support, he merely said to wait for the answer," Muhyiddin said.

Australian Associated Press