Federal independent Senator Nick Xenophon has been detained by Malaysian authorities.
He was taken into custody on his arrival at Kuala Lumpur airport and told he was considered a security risk.
Senator Xenophon had been about to join a delegation which had meetings planned with Malaysian opposition members and officials with the electoral commission on Monday and Tuesday.
The South Australian senator is outspoken on human rights issues in Malaysia.
The ABC's Lyndal Cutris spoke to him shortly after he had been detained.
"He said he's under escort. He can't go to the bathroom without a guard and he says that the Australian High Commissioner to Malaysia is on his way to the airport," she said.
"I don't think he was completely allowed to use his phone. He was speaking to try and get the news out about what had happened to him."
Senator Xenophon was last year during a fact-finding mission.He had arrived in Malaysia today, ahead of other members of the delegation.