He told former ministers that they could not leave the country and had to hand over their official vehicles to the military.
Col Doumbouya also urged mining companies to continue their operations in the country, adding that they would be exempt from the ongoing nationwide curfew.
Guinea is one of the world’s biggest suppliers of bauxite, a necessary component of aluminium. Following the coup, prices of aluminium climbed to their highest in more than a decade due to concerns over supplies.
They said regional governors had been replaced by military commanders, and the ousted 83-year-old president was safe but in detention.
Col Doumbouya said his soldiers had seized power because they wanted to end rampant corruption and mismanagement.
President Condé was re-elected for a controversial third term in office amid violent protests last year.
The veteran opposition leader was first elected in 2010 in the country’s first democratic transfer of power. Despite overseeing some economic progress, he has since been accused of presiding over numerous human rights abuses and harassment of his critics.
After the coup was announced, hundreds of residents poured into the streets of Conakry to celebrate the takeover, climbing onto military vehicles to greet soldiers draped with Guinean flags.
Mamoudou Nagnalen Barry, a founding member of the opposition FNDC (National Front for the Defence of the Constitution), told the BBC that he had mixed emotions about the coup, but that he mostly welcomed it.
“I will say that I’m sadly happy with what happened,” he said.
“We don’t want to be happy with a coup, but in certain circumstances like [the ones] in Guinea now, we will say we are really happy with what is happening because, without that, the country will be stuck in [the] endless power of one person who wants to stay in power forever.”
Mr Barry added he hoped the soldiers would hand power back to civilians.
Guinea’s coup is the fourth time West Africa has witnessed an attempt to undermine democracy in the region since August 2020. There have been two military takeovers in Mali and a failed attempt in Niger.