[4][5] He was retained as Minister of National Education in a cabinet reshuffle on 21 May 1992, and was additionally given responsibility for science, technology, youth, sports, culture, and the arts.
[12] Speaking on Radio France Internationale in May 2000, Koumba alleged that former Prime Minister Bernard Kolelas, a political enemy of Sassou Nguesso who was living in exile, was a murderer.
[19][20] Koumba's election was in accordance with a custom that the post should be held by a southerner, and he was viewed as more reliably loyal to President Sassou Nguesso than the previous head of the legislature, Thystère Tchicaya.
"[24] In October 2010, Koumba visited Iran and met with Iranian President Mahmoud Ahmadinejad, saying that he hoped for greater cooperation between the two countries.
[25] In the July–August 2012 parliamentary election, Koumba was re-elected to the National Assembly as the PCT candidate in Banda constituency; he won the seat in the first round, receiving 62.71% of the vote.
[30][31] Central African Prime Minister André Nzapayéké met with Koumba in Brazzaville on 14 February 2014 to discuss the situation in his country and to express gratitude to the Congolese people for the role played by Congo-Brazzaville in the crisis.
[32] During a visit by Sassou Nguesso to Niari in March 2014, Koumba, together with Pierre Mabiala, urged the President to embrace a proposal to change the constitution so that he could stand for another presidential term in 2016.
[33][34] Soon afterward, on 6 April 2014, an organization intended to mobilize support for the proposal, the Citizen Front for Changing the Constitution, was established with Koumba as its President.
"[37] In the July 2017 parliamentary election, he was re-elected to the National Assembly as the PCT candidate in Banda, winning the seat in the first round with 99% of the vote.