Gabon's new military leader has pledged to return the country to democracy, but has refused to provide a timelines for fresh elections.
Gen Brice Oligui Nguema said the country's state institutions would be made more democratic and their suspension was only "temporary".
But Gabon's opposition coalition says the military shows no signs of handing power back to a civilian government.
The deposed president, Ali Bongo, was placed under house arrest this week.
Army officers appeared on state TV in the early hours of Wednesday to say they had seized control, ending the Bongo family's 55-year hold on power in the central African state.
They said they had annulled the results of Saturday's presidential election, in which Mr Bongo was declared the winner but which the opposition said was fraudulent.
In a televised address on Friday evening, Gen Nguema said the military would move "quickly but surely" to avoid elections that "repeat the same mistakes" by keeping the same people in power.
"Going as quickly as possible does not mean organising ad hoc elections, where we will end up with the same errors," he said.
Gabon's main opposition group, Alternance 2023, which says it is the rightful winner of Saturday's election, urged the international community on Friday to encourage a return to civilian rule.
"We were happy that Ali Bongo was overthrown but ... we hope that the international community will stand up in favour of the Republic and the democratic order in Gabon by asking the military to give back the power to the civilians," Alexandra Pangha, a spokesperson for Alternance 2023 leader Albert Ondo Ossa, told the BBC.
She added that the plan for Gen Nguema to be sworn in as transitional president on Monday was "absurd".
The coup in Gabon is the eighth in west and central Africa since 2020, following Niger, Mali, Guinea, Burkina Faso and Chad.
It has been condemned by the UN, the African Union and France - its former colonial power which had close ties to the Bongo family.
Mr Bongo, who had been in power since 2009, appeared in a video at his home this week calling on his "friends all over the world" to "make noise" on his behalf.
But his removal has also been celebrated by many in Gabon who have grown resentful of his, and his family's, regime.
Crowds in the capital, Libreville, and elsewhere were seen celebrating the army's declaration earlier this week.