(CNN) -- Security has been stepped up around a prominent Australian Muslim leader after Twitter threats from a Sydney-based militant seen in recent photos clutching severed heads in Syria. In a tweet that's since been deleted, a man believed to be Mohamed Elomar offered $1,000 for information on the whereabouts of Dr. Jamal Rifi and his five children. "Anyone in Sydney who can give me the details of Habashi dog Dr Jamal Rifi, anything, house details, wat area am willing to pay $1000," the tweet said. Rifi is a general practitioner and outspoken community leader who this week condemned shocking images posted on social media by convicted terrorist Khaled Sharrouf of his seven-year-old child holding a mutilated head.
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Australian tweets bounty for information on outspoken Muslim leader
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Mohamed Elomar is believed to be in Syria, fighting with ISIS
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Elomar posted photos of himself holding severed heads of fighters
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Sharrouf shocked world with photo of young son holding mutilated head
Mohamed Elomar
Mohamed Elomar
Elomar
The senior @placeholder is currently serving a minimum 21-year sentence for the plot, which involved the manufacture of explosives for a "potentially catastrophic" attack.
Mohamed Elomar
Mohamed Elomar
Elomar
The latest tweets attributed to @placeholder came from the now suspended Twitter handle @abu hafs ozzie.
Jamal Rifi
Jamal Rifi
Rifi
@placeholder followed in the early 1980s and has become a respected member of the community for his efforts in breaking down religious barriers.
Jamal Rifi
Jamal Rifi
Rifi
Mohamed's father would support him "100%," @placeholder said, though he added he hadn't spoken to him since the threats were made.