The former crown prince of Jordan is accused of trying to mobilise tribal leaders against the government, the country's deputy prime minister says.
Prince Hamzah bin Hussein worked with "foreign entities" to destabilise the state, Ayman Safadi said.
The prince had earlier released two videos to the BBC, in which he claimed he was being held under house arrest.
He denied conspiracy, but accused Jordan's leaders of corruption and incompetence.
Sixteen people, including a former adviser to King Abdullah and another member of the royal family, were arrested on Saturday for allegedly threatening security.
In his videos, Prince Hamzah, the king's half-brother, said he had been told he could not go out or communicate with people.
The move is thought to follow a visit by the prince to tribal leaders, where he is said to have garnered some support.
His mother, American-born Queen Noor, has said she is praying for what she called innocent victims of "wicked slander".
What is the prince accused of?
Responding to the fallout on Sunday, deputy prime minister Safadi said Prince Hamzah had used the videos to distort facts and incite empathy, according to the state news agency, Petra.
He told a news conference that the prince had been liaising with foreign parties about destabilising the country and had been being monitored for some time.
The prince is accused of seeking to mobilise "clan leaders" against the government.
But the plot had been "nipped in the bud", Petra quoted the deputy PM as saying.
Safadi went on to allege that a man with links to foreign security services had offered Prince Hamzah's wife, Princess Basmah, a flight out of Jordan. He did not specify which foreign security service was apparently involved.
Safadi said officials had tried to discourage the prince rather than take legal action against him, but that Prince Hamzah had "dealt with this request negatively". He noted that dialogue was ongoing.
Regional powers including Egypt, Turkey, and Saudi Arabia have voiced support for King Abdullah in the wake of the operation.
The United States, which is allied with Jordan in its campaign against the Islamic State (IS) group, described the monarch as a key partner who has its full support.
The UK also backed the king. "The Hashemite Kingdom of Jordan is a greatly valued partner for the UK," said James Cleverly, minister for Middle East and North Africa.
What's behind this?
Tensions within the royal household had been visible for some time, Jordanian journalist Rana Sweis told the BBC.
"The former crown prince is also seen as popular. He has a very candid resemblance to his father, King Hussein, and he is also very popular with the local tribes," she said.
Praying that truth and justice will prevail for all the innocent victims of this wicked slander. God bless and keep them safe.— Noor Al Hussein (@QueenNoor) April 4, 2021
Another member of the royal family waded into the row on Twitter on Sunday night, hitting out at Queen Noor and suggesting it was a dispute over succession rights.
"Grow up Boys," posted Princess Firyal, the ex-wife of the brothers' uncle, Prince Muhammad bin Talal.
But some commentators said the prince's criticism of corruption in the kingdom struck a chord with many in the country.
"What Prince Hamzah said is repeatedly heard in the homes of every Jordanian," said Ahmad Hasan al Zoubi, a prominent columnist.
Jordan has few natural resources and its economy has been hit hard by the Covid-19 pandemic. It has also absorbed waves of refugees from the civil war in neighbouring Syria.
However, high-level political arrests are rare. The country's powerful intelligence agency has gained extra powers since the pandemic began, drawing criticism from rights groups.
Who is Prince Hamzah?
The oldest son of the late King Hussein and his favourite wife Queen Noor, Prince Hamzah is a graduate of the UK's Harrow School and the Royal Military Academy at Sandhurst. He also attended Harvard University in the US and has served in the Jordanian armed forces.
He was named crown prince of Jordan in 1999 and was a favourite of King Hussein, who often described him in public as the "delight of my eye".
However, he was seen as too young and inexperienced to be named successor at the time of King Hussein's death.
Instead his older half-brother, Abdullah, ascended the throne and stripped Hamzah of the title of crown prince in 2004, giving it to his own son.
The move was seen as a blow to Queen Noor, who had hoped to see her eldest son become king.
Who else has been arrested?
Others detained on Saturday include Bassem Awadallah, a former finance minister, and Sharif Hassan Bin Zaid, a member of the royal family.
Awadallah, an economist who was educated in the US, has been a confidant of the king and an influential force in Jordan's economic reforms.
He has often found himself pitted against entrenched government bureaucracy resistant to his plans, observers say.
No members of the armed forces were said to be among those detained over the alleged plot.