Jakarta. Police are investigating a threat to kill President Joko "Jokowi" Widodo made by an unidentified man in a video that has been doing the rounds on social media since Saturday.

The video, posted on Facebook and forwarded via WhatsApp, shows a young man saying that he would behead the incumbent president.

"From Poso [in Central Sulawesi], [I am] ready to behead Jokowi… Jokowi, prepare to be slaughtered… God willing," he says, with a crowd responding with chants of Allahu akbar [God is greatest].

Member of Jokowi Mania, a supporters' group, reported the threat to the Jakarta Police on Saturday.

"We have reported the person who has threatened the head of state, or president, with a very terrifying act," Jokowi Mania leader Immanuel Ebenezer said, as quoted by BeritaSatu.com.

He said the video was most likely taken in front of the offices of the Election Supervisory Agency (Bawaslu) in Central Jakarta by supporters of presidential candidate Prabowo Subianto and his running mate Sandiaga Uno.

Jokowi Mania also filed a report against the person who recorded the video and two women seen with the young man when he made the threat.

"Why are we confident that they are most likely Prabowo supporters? Because they participated in a rally in front of the Bawaslu offices. It is dangerous if any threats, let alone death threats, are made during a political rally," Immanuel said.

"It's fine to have different political aspirations, but using death threats is dangerous. It cannot be allowed," he told reporters in front of the Jakarta Police headquarters.

Supporters of Prabowo and Sandiaga held a rally in front of the Bawaslu offices on Thursday, Friday and Saturday to call on the agency to disqualify Jokowi and Ma'ruf Amin, his running mate in the April 17 presidential election.

"We're investigating the case," Jakarta Police spokesman Chief Comr. Argo Yuwono, said.

The General Elections Commission (KPU) is scheduled to announce the official results of this year's simultaneous presidential and legislative elections on May 22. As of Saturday evening, and with nearly 78 percent of the ballots counted, Jokowi-Ma'ruf had secured 56.3 percent of the vote against the 43.7 percent of Prabowo-Sandiaga.

Prabowo previously declared that he had won 62 percent of the vote, without substantiating his claim.

Quick counts by reliable pollsters all favored Jokowi-Maruf, while the candidate pair's campaign team said more than 80 million of the votes so far counted, or more than 50 percent of the total, were in their favor.