A former top adviser to Jordan’s King Abdullah II and a relative of the monarch have pleaded not guilty to sedition and incitement charges, a defence lawyer said.

The highly anticipated trial was held under tight security and was closed to the media.

The charges revolve around an unprecedented public rift in the traditionally discreet royal family. The defendants are accused of conspiring with a senior royal – Prince Hamzah, a half-brother of the king – to foment unrest against the monarch while soliciting foreign help.

Hamzah is not facing charges, with the king having said the royal family is handling the matter privately. Yet he is the central figure in the case, and defence lawyers said they plan to call him to the stand.

Since the drama erupted into the open in early April, with Hamzah being placed under house arrest, clashing narratives have swirled around the popular prince. He is either a champion of ordinary Jordanians suffering from economic mismanagement and corruption, or a disgruntled royal who never forgave Abdullah for taking away his title of crown prince in 2004.

The indictment, read in court on Monday, alleges Hamzah was driven by personal ambition and determined to become king. It says the prince and the two defendants – Sharif Hassan bin Zaid, a royal, and Bassem Awadallah, a former royal adviser – conspired to stir discontent.

Awadallah, who has Jordanian, US and Saudi citizenship, held senior posts in Jordan, including head of the royal court and planning minister. Later, he served as the king’s official envoy to Saudi Arabia and has close ties to Saudi Arabia’s powerful crown prince, Mohammed bin Salman.

Bin Zaid is a distant cousin of the king.

They are the most senior establishment figures to appear before the security court, which typically goes after drug offenders or suspected militants.

Defence lawyer Mohammad Afeef, who represents Awadallah, told journalists waiting outside the state security that the two defendants entered “not guilty” pleas. He said the court heard two prosecution witnesses, and that another session would be held on Tuesday.

A video leaked from inside the court shows Awadallah, wearing the light blue uniform of detainees and a face mask as he was being led by guards through a room in the court. State media ran the footage and stills photos of Awadallah on their websites.

Since the royal rift became public, it has broken taboos in Jordan and sent jitters through foreign capitals, with Western powers rallying behind Abdullah, an indispensable ally in an unstable region.

The case exposed rivalries in Jordan’s Hashemite dynasty and spawned unprecedented public criticism of the monarch.