Jordan's foreign minister has accused King Abdullah's half-brother of conspiring with foreign parties in a plot to destabilize the country.
Ayman Safadi raised the allegation against Prince Hamzah bin Hussein at a news conference in the capital, Amman, on Sunday.
Safadi said Prince Hamzah has been under investigation, and that more than 10 others, including royal members close to the prince, have been arrested.
Safadi did not elaborate on details of the plot or the foreign elements. But he said initial investigations showed that their "activities and movements had reached a stage that directly affected the security and stability of the country."
Prince Hamzah became crown prince in 1999 when King Abdullah ascended the throne. But the prince was stripped of the title in 2004, raising speculation that his ties with the King were strained.
Prince Hamzah denied any wrongdoing in a video passed to the BBC. He said he has been placed under house arrest.
It is rare for Jordan, a US ally with a reputation as a stable monarchy, to be involved in political instability.
The United States and Middle Eastern countries issued statements supporting King Abdullah. Analysts say they are closely watching the situation in Jordan and hoping it will not destabilize.