The late leader's son, Defence Minister Ali-Ben Bongo, is tipped to replace him
No current or former member of government should stand in forthcoming presidential elections in Gabon, say civil society groups in the country.
A correspondent in Gabon says the organisations are particularly concerned the son of the late President, Omar Bongo, will take over.
Mr Bongo, who ruled Gabon for more than four decades, died after a long illness in a Spanish hospital last week.
Elections are due to be held in the West African nation within 45 days.
Interim President Rose Francine Rogombe has been sworn in as the nation's first female leader - she is constitutionally ineligible to stand for election.
Gabonese reporter Linel Kwatsi in the capital, Libreville, told the BBC that civil society groups want the interim leader, who is a member of the ruling party, to guarantee the poll will be free and fair.
They also say members of the government have used state funds to run election campaigns in the past.
The ruling Gabonese Democratic Party has been deciding who should succeed the late president, with his 50-year-old son, Defence Minister Ali-Ben Bongo, tipped as a leading contender.
Mr Bongo is to be buried at Franceville in the Bateke region of his birth in south-east Gabon on Thursday.
At least 10 heads of state, including French President Nicolas Sarkozy, are expected to attend the funeral.
Under Mr Bongo, Gabon kept close economic and political ties with the former colonial power, France.
It emerged last month that Mr Bongo was being treated in a Barcelona clinic, amid unconfirmed reports he had cancer.
The government said on Monday of last week that the 73-year-old had died of a heart attack, hours after saying he was alive and well.