Abiola's daughter Hafsat: "Very sceptical"

His daughter Hafsat has blamed the military government which kept her father prisoner for four years for his death.

"We have been trying for 18 months to get my father access to his doctor," said Hafsat Abiola.

"We now know why it was so important to keep his condition secret from the people.

"(He died) either because medical neglect brought on a heart attack or because they poisoned him."

Soyinka says Abiola was murdered

Ola Soyinka, a Nigerian political activist, also believes Chief Abiola was murdered.

"It is not beyond the bounds of medical possibility that just prior to the meeting something was administered," he told BBC World.

He also called into question the impartiality of the planned post mortem that is to be carried out.

Mr Soyinka said a clique in Nigeria was desperately clinging to power.

He said: "We are beginning to see the rather sinister power games moving into a dangerous phase where the future of Nigeria as a united state is going to be put in great doubt."