Johannesburg: The family of four Indian-origin South African siblings detained in Saudi Arabia for the past month without charge has appealed to President Jacob Zuma to intervene to secure their release.

According to Nazir Desai, Saudi authorities have declined to say why his sons Waliullah and Wasiullah, both lecturers in Arabic studies, and their sisters Huddah and Thembi, both students in Saudi Arabia, have been in custody for more than a month without being charged.

Jacob Zuma. File pic/AFP

Desai said his children, all in their twenties, were arrested when they returned to Saudi Arabia on November 23 after a short holiday at home. Wasa Al-Nafjan, deputy secretary at the Saudi consulate in Pretoria, would not comment on rumours that the four were arrested because of allegations of terrorism amid speculation locally that the siblings were detained because of attempts to join IS.

"It has to do with an investigation into security issues," Al-Nafjan told the Afrikaans weekly Rapport, adding that she could only comment once they had been charged or released after a hearing. Brian Dube, spokesperson for the South African Department of State Security, confirmed to the weekly that the Desai siblings were being detained due to an investigation into "security issues".

Ahmed Sadek Desai, a cousin of the father, told the Post newspaper in his hometown of Port Elizabeth that the CIA had held and questioned him in 1999 in Bangladesh about his suspected involvement in the funding of al-Qaeda. The cleric denied any involvement and was released after several weeks.

The cousins Ahmed and Nazir Desai are both linked to the Darul Uloom Abu Bakr Islamic Institute of Education, which has earlier been outspoken about its support for IS despite all other major Islamic bodies in South Africa decrying the actions of the militants as being un-Islamic.

The two were also accused in 2007 of being involved in an alleged jihadist training centre in Port Elizabeth, something described at the time by the South African National Intelligence Agency as "pure speculation".

Zuma's office was unavailable for comment, but political analysts here are of the view that he was unlikely to intervene, preferring to let the diplomatic channels of the foreign ministry handle the matter.