He expressed the condolence in a statement issued by his Media Aide, Mr Paul Ibe, on Sunday in Abuja.
Abubakar said that he received with sadness report of the loss of Mrs Christy Dungtou and Mr Donatus Morkwap, members of one of his support groups, in a road accident on their way to Shendam after the Jos rally.
Mrs Dungtou died at the scene of the accident while Morkwap passed away as he was being conveyed to General Hospital, Barkin-Ladi.
Mr Kwalmi Julius, one of the injured whose condition is critical is receiving treatment at the Plateau Hospital, Jos, while the other two had been referred to Shendam.
The statement revealed that the Atiku Presidential Campaign is in liaison with an official of the support group who has confirmed that the corpses of the deceased have been deposited at the mortuary in Shendam Local Government Area of Plateau.
Abubakar expressed his condolences to the families of the deceased even as he prayed for the speedy recovery of those still in hospital.
The former Vice President has also directed his campaign organisation to spare no resource in ensuring that those still in hospital receive the best of medical care.
He has also instructed that the Campaign takes care of the burial cost of the deceased.
Abubakar acknowledged the efforts and sacrifices of thousands of his support groups and millions of their members in his avowed commitment to get Nigeria working again for the good of all.
He assured that their sacrifices would not be in vain.