Jordan has accused a former crown prince Prince Hamzah bin Hussein of plotting with foreign and local parties to destabilise the western ally as divisions within the ruling family in the normally stable country burst into the open.

Ayman Safadi, Jordan’s foreign minister, told reporters that the alleged plot by Prince Hamzah, a half-brother of King Abdullah and heir apparent until his demotion in 2004, and others had been contained.

Safadi said people around Prince Hamzah had communicated with parties calling themselves “external opposition” and contact had been made with “foreign entities,” according to Petra, Jordan’s state news agency. A man linked to a foreign security service had contacted Prince Hamzah’s wife to offer a plane to fly them out of the kingdom.

“Initial investigations showed these activities and movements had reached a stage that directly affected the security and stability of the country,” Safadi said on Sunday. “The investigations had monitored interferences and communications with foreign parties over the right timing to destabilise Jordan.” He did not elaborate on what he meant by foreign parties and entities.

Safadi’s comments will intensify the intrigue about an extraordinary 48 hours in a normally stable country and staunch ally of the west. Prince Hamzah released a video on Saturday claiming he had been placed under house arrest. Major General Yousef Huneiti, the army chief, denied the former crown prince had been detained but said he had been warned to stop “activities” used to target the nation’s security and stability.

Huneiti also said Bassem Awadallah, a former finance minister and chief of staff to King Abdullah, and Sharif Hassan bin Zaid, a distant member of the royal family, have been arrested. Awadallah has in recent years been an adviser to Saudi Crown Prince Mohammed bin Salman. Safadi said 16-18 people had been arrested in connection with the alleged plot.

The events raise concerns about the stability of Jordan, which borders Israel, Iraq and Syria. King Abdullah, who is feted in Washington and London, is also considered to be an important voice of moderation in the Middle East.

Some analysts believe the saga reflects divisions within the ruling family. Others suspect it could be King Abdullah reacting to complaints of corruption and poor governance as social and economic pressure mount in the resource-poor country.

In the video released on Saturday, the former crown prince launched an attack against the ruling system, accusing it of corruption, nepotism and misrule.

Prince Hamzah said he made the recording to make it clear that he was not part of any “conspiracy or nefarious organisation or foreign-backed group”.

“What you see and hear in terms of the official line is not a reflection of the realities on the ground,” he said. “I’m not the person responsible for the breakdown in governance, for the corruption and for the incompetence that has been prevalent in our governing structure for the last 15 to 20 years, and has been getting worse by the year.”

Safadi said Prince Hamzah’s videos distorted the facts and that King Abdullah would talk directly to Prince Hamzah and deal with the matter within the family. In a further sign of tensions within the royal family, Queen Noor, Prince Hamzah’s mother, took to Twitter on Sunday to describe the allegations against her son as “wicked slander”.

Lina Khatib, director of the Middle East programme at Chatham House, said Saturday’s events appeared to be related to a power struggle within the royal family.

“In western policy circles there have been concerns about political stability in Jordan and this appears to confirm that tensions within the regime and the royal family have been going on for some time,” she said. “The west views King Abdullah as a reliable ally and it’s not in their interests to see instability in Jordan.”

King Abdullah, who has ruled since the death of his father in 1999, is generally perceived to enjoy strong support among Jordanians.

A spokesman for the US state department said Washington was closely following the reports and in touch with Jordanian officials. Regional allies, including Saudi Arabia, were swift to express their support for King Abdullah. Iran on Sunday said it backed “peace and stability” in Jordan.

Amman has long depended on financial support from western and Gulf states and it is grappling with declining revenues and debts that have soared to about 100 per cent of gross domestic project.