KUALA LUMPUR (AFP) - Malaysia's Prime Minister Najib Razak has taken ill with signs of chickenpox and may be unable to meet visiting dignitaries this week, official spokesmen said late Sunday.

Najib is scheduled to meet Australia's Prime Minister Julia Gillard Monday and US Secretary of State Hillary Clinton in Kuala Lumpur Tuesday, after all three attended the ASEAN summit in Hanoi at the weekend.

"The prime minister is ill and the doctors have advised him to cancel all meetings and appointments," Najib's press secretary Tengku Sharifuddin Tengku Ahmad told AFP.

Government media adviser Jalaludin Bahaudin told state media Najib felt unwell and had developed rashes, muscular aches and joint pains on the last day of the ASEAN summit.

"On arrival in Kuala Lumpur today, he showed early signs of chickenpox and was immediately started on appropriate treatment," Jalaludin said.

Jalaludin told AFP that the visits by Gillard and Clinton to Kuala Lumpur were expected to go ahead despite Najib's illness.

"The visits are still on. The Australian Prime Minister is in Malaysia and our deputy Prime Minister Muhyiddin Yassin will take the PM's place at Monday's meetings," he said.

"We are still working on what will happen with Clinton's visit but the foreign minister will most likely stand in and that visit should also take place," he added.

Jalaludin told state media that Najib had immediately begun receiving "appropriate treatment" for chickenpox after his return to Kuala Lumpur

"As medication was started early, the prime minister has responded well," he added.

The Australian High Commission and the US Embassy could not be reached for comment.