A man has been arrested for threatening lawyer Siti Kasim, Kuala Lumpur police chief Amar Singh said. 

"Yes we can confirm that a male Malay has been arrested regarding the case," he told reporters today.

The suspect was arrested last night and remanded for three days, he said. 

Siti earlier lodged a police report over death and rape threats allegedly made against her online following an article on her support of the lesbian, gay, transgender and bisexual community. 

She said there were also threats to behead her and attack her with acid. 

The man allegedly urged Muslim groups, including "silat organisations which have taken oaths to defend Islam" to unite to "behead" Siti. 

"Instead of fighting with each other on worldly issues, why don't we 'behead' this fat pig with hair the colour of rust first, before Allah scorns us," he allegedly said. 

A screenshot of his posting was shared by Siti on her Facebook page. 

Those commenting on the man's posting ask for Siti's address and share their phone numbers to be contacted for any action against Siti.

"Just splash acid on her face, end of the story," said one commenter. 

Another commenter called for "that pig to be tied up" so they can stone her. 

"Let her feel pain in the world before she enters the after life," he said.