Nigerian President Olusegun Obasanjo has accused his estranged deputy of wishing him dead and consulting Islamic holy men on the date of his demise.
Mr Abubakar said the president's mind was "full of the cobwebs of juju"
Mr Obasanjo said the vice president had told a former minister: "Don't worry, the president will be dead soon."
VP Atiku Abubakar denied the charges, saying Mr Obasanjo's mind was full of "the cobwebs of juju or occult".
The pair fell out when Mr Abubakar opposed the president's efforts to stay in office for a third term.
Mr Abubakar ran in last month's presidential elections as an opposition candidate, despite spirited efforts by Mr Obasanjo to stop him.
According to official results Mr Abubakar lost to the governing party's Umar Yar'Adua, who succeeds Mr Obasanjo as president next week.
'I will be president'
Speaking about the feud between him and his deputy on national television, Mr Obasanjo said Mr Abubakar had told a minister that he had been consulting a marabout (holy man).
President Obasanjo is standing down after two terms
The president said Mr Abubakar told the minister: "So the same marabout has told me that I will be President when this man (Obasanjo) dies and had given me a month that he will die, you better prepare."
Mr Obasanjo said the alleged comments showed his rival's "bankruptcy of ideas, bankruptcy of knowledge and lack of knowledge in God and the affairs of God on the lives of human beings".
He added: "If I will live for another 20 years, it is in the hands of God. I am not afraid of such stupidity. Of course, I know that you can be poisoned but if God wants to save you, you will be saved."
Mr Abubakar fell out with Mr Obasanjo after he publicly opposed attempts to change the constitution to give the president a third term.
The vice-president who stands down next week with Mr Obasanjo dismissed the president's accusations as "bizarre and ludicrous".
"Unlike Obasanjo who uses Christianity as a smokescreen while engaged in occultism and diabolical acts, I am a devout Muslim who has always striven to live in accordance with the teachings of Islam," Mr Atiku fired back in a statement.
"The next occupant of the State House (presidential villa) will need to spiritually cleanse the presidential lodge to make it habitable for normal people.
"I don't believe in resorting to marabout and have never wished the president dead. Rather, it is the president who has been hell-bent on eliminating me politically and physically.
"By making public accusations of fetish acts against me, the president has exposed his own mindset as one that is covered in the cobwebs of juju or occult.
"It is on record that the president had never in the past denied his association with deadly secret societies."