New details have emerged about the abductions of three dissident Saudi princes in what appears to be a systematic state-run Saudi government programme to kidnap defectors and dissidents.

The three, all members of the Saudi regime before they became involved in peaceful political activities against the government in Riyadh, were kidnapped and taken against their will to Saudi Arabia between September 2015 and February 2016.

Their story, which was originally reported by the Guardian in March 2016, is the subject of a BBC Arabic documentary to be broadcast this week called Kidnapped! Saudi Arabia’s Missing Princes.

The most senior of the princes, Prince Sultan bin Turki, was kidnapped by the Saudis on 1 February 2016 together with about 20 members of his entourage, many from western countries.

In the documentary, two westerners in the prince’s entourage describe the moment they realised the plane they were travelling on was not landing in Cairo as planned, but had instead been diverted to Riyadh.

The westerners describe Prince Sultan screaming and fighting with the Saudi flight attendants, who produced concealed weapons in order to subdue him and control the other passengers as the plane touched down.

They said when the plane landed it was immediately surrounded by dozens of cars and military vehicles, as well as heavily armed Saudi soldiers and police. The prince was dragged kicking and screaming from the plane into an unmarked car, shouting to his entourage that they were all being kidnapped and that they should alert their embassies. The prince has not been seen in public since.

The rest of his entourage, which included a number of young female westerners, were then held for three days in Saudi Arabia.

First, all their electronic devices and passports were confiscated. Then they were escorted to a Riyadh hotel by Saudi soldiers, among whom were several of the flight attendants from the plane now wearing Saudi military uniforms and armed with machine guns.

Under constant armed guard, without their passports and, in the case of the women, without the proper attire to go outside, there was no way they could leave.

Their phones and electronic devices were later returned with all pictures and evidence of their kidnapping wiped – except one picture that had been missed.

Interior of the plane Prince Sultan was travelling on, taken by a member of his entourage. Saudi authorities deleted all other pictures of the plane.

On the third day the westerners were marched one by one into a room at the hotel by heavily armed Saudi soldiers where a Saudi military officer apologised for the inconvenience before making them sign documents in Arabic which they did not understand.

Their kidnappers then asked them where they wanted to travel. Later they were brought one by one to the airport, walked through security and on to a plane minutes before takeoff and then had their passports returned.

The documentary also presents new evidence about the previous alleged kidnap of Prince Sultan in 2003, including a medical record from King Faisal hospital in Riyadh.

The medical report indicates the prince was aspirated and intubated in Geneva before being put on a medevac plane to Saudi Arabia, which is consistent with the prince’s claim that he was traumatically injected on the side of his neck as he was violently abducted by five masked men.

One British member of the prince’s entourage describes how hours after the prince was kidnapped the Saudi ambassador in Geneva arrived at the prince’s suite in the Intercontinental hotel in Geneva to tell his entourage they should all get out as the prince was now in Riyadh.

There has been no attempt by the Swiss government or any western authority to try to get access to Prince Sultan or any of the kidnapped princes in Saudi Arabia.

The criminal case for kidnap that Prince Sultan is pressing in Geneva against two senior Saudi officials – Prince Abdulaziz bin Fahd and the minister of Islamic affairs, Saleh al-Sheikh – remains open.

The documentary also reveals new details about the abduction of another dissident, Prince Turki bin Bandar. Prince Turki is a former senior police officer whose responsibilities once included policing the royal family.

In the documentary, a friend of Prince Turki presents a note the prince wrote to him before he disappeared in 2015, saying he feared the Saudi government was going to kidnap or assassinate him.

The Moroccan newspaper As Sabah reported that in November 2015 Prince Turki was arrested and detained at Sala prison in Morocco as he was leaving to return to France.

A few days later Prince Turki was deported to Saudi Arabia at the request of the kingdom’s authorities.

In the documentary, a friend of a third disappeared prince, Saud bin Saif al-Nasr, tells how he too said before he disappeared that he thought the Saudis were going to kidnap or assassinate him for his opposition activities.

In 2015 Prince Saud was approached by a Russian-Italian business consortium which asked him to be their business partner in exchange for a fee. They persuaded him to board a private plane to Italy where he thought he was going to a business meeting to finalise the contract. Like the other princes, he has not been seen or heard of since.

The Saudi and Moroccan authorities have made no comment in response to the new evidence.