Former Gujarat home minister Amit Shah, considered a close aide of chief minister Narendra Modi, has been called to Delhi for questioning by the CBI in connection with the 2006 fake encounter of Tulsiram Prajapati, a key witness to the killing of Sohrabuddin Sheikh and his wife Kausarbi.

CBI asked Shah, who is out on bail after being arrested in the Sohrabuddin case, to appear at the agency headquarters for questioning in the Prajapati case.

The interrogation is expected to be held as early as Tuesday during which CBI is expected to confront the BJP leader with telephone records about him being allegedly in touch with police officers including the deputy inspector general of police (jail) D G Vanzara.

Shah has been asked by the supreme court not to enter Gujarat as the agency alleged that he may tamper with the evidence or intimidate the witnesses.

Prajapati, a close aide of Sohrabuddin, a gangster, was killed in an alleged shoot-out near Chapri village in Banaskantha district on December 28, 2006.

CBI took over the case last April following direction from supreme court and registered a case against "police officials of Gujarat and Rajasthan and others for alleged involvement in the criminal conspiracy of wrongful restraint, wrongful confinement, abduction and murder of Tulsi Prajapati and causing disappearance of evidence".

The FIR was registered following supreme court's order on April 8 last on a writ petition filed by Narmada Bai, Prajapati's mother.

Bai's petition formed the basis of the FIR, and the probe was being conducted by the special investigation team (SIT) of CBI officers which had earlier probed the Sohrabuddin Sheikh case.

Bai had alleged that her son was killed in a fake encounter by the Gujarat police as he was a key eyewitness in the November 2005 killing of Sohrabuddin Sheikh.

CBI also sought help of the forensic experts in reconstructing the alleged fake encounter of Prajapati by Gujarat police in 2006.

The CBI had questioned Yashpal Chudasama and Ajay Patel, two police officers believed to be close to Shah in the last week of December for about four hours.

CBI has shown Chudasama and Patel, along with Shah, as accused in the charge sheet they filed in the Soharabuddin case. They have been accused of trying to influence witness and derail CBI probe in the Sheikh encounter case.