Jordan's former Crown Prince Hamza Bin Hussein said in a video recording yesterday he was under house arrest and had been told to stay at home and not to contact anyone, Reuters reported.
Hamza issued the recording after news that the country's military had told him to halt actions used to target the country's "stability and security". Army chief Yusef Huneity earlier denied reports that Hamza had been arrested.
Hamza said in the video, passed by his lawyer to the BBC, that he was not part of any foreign conspiracy and denounced the ruling system as corrupt.
"Its a very sad and unfortunate turn," he added.
"[Jordanians'] well being has been put second by a ruling system that has decided that its personal interests, financial interests, that its corruption is more important than the lives and dignity and future of the ten million people who live here," he said.
Two people familiar with the situation told Reuters security forces had arrived at his small palace and begun an investigation. King Abdullah dismissed Prince Hamza as heir to the throne in 2004 in a move that consolidated his power.
The Washington Post said Jordanian authorities detained the former crown prince and arrested nearly 20 other people after what officials called a "threat to the country's stability".
A former US official with knowledge of events in Jordan said the plot, which he described as credible and broadbased but not imminent, did not involve a "physical coup". Rather, he said, those involved were planning to push for protests that would appear to be a "popular uprising with masses on the street" with tribal support.
Jordan would investigate whether there was a foreign hand in the plot, said the former US official.
This comes after news that Jordanian security forces arrested a former adviser to King Abdullah, a member of the royal family and others on "security related" grounds, the Petra state news agency said.
US-educated Bassem Awadallah, a long-time confidant of the king who later became minister of finance, and Sharif Hassan Ben Zaid, a member of the royal family were detained along with other unnamed figures, Petra said. It gave no details.
Awadallah, who was a driving force behind economic reforms before he resigned as chief of the royal court in 2008, has long faced stiff resistance from an old guard and an entrenched bureaucracy that flourished for years on government perks.