Authorities released photos of Bongo meeting the heads of the Constitutional Court and National Assembly and his chief of staff.
Washington says it wants to send a clear signal of the need for accountability in the DRC
"We reaffirm our faithfulness and our loyalty to His Excellency Joseph Kabila Kabange, honorary president of the Republic."
Doumbia, the most senior government representative in the commune, was abducted in May 8 last year.
According to provisional results, Kabila's supporters won 337 out of the parliament's 485. Tshisekedi's own party only garnered 32 seats.
The action comes after gunmen abducted two of MSF's local staff earlier this month.
Officials say everything will be put in place for them to "resocialise, learn the spirit of patriotism and public duty"
The charge is punishable by death
The former government minister was arrested in the economic capital Douala late last month.
A man from the city of Bambari was held by Russians and repeatedly tortured, according to the UN report