The swearing-in was done on Wednesday at the Government House in Port Harcourt, the state capital amid tight security.
The swearing-in comes a day after he forwarded the list to the state House of Assembly led by factional Speaker, Victor Jumbo.
It will be recalled that the lawmakers had invited the nominees for screening as early as 8 am on Wednesday.
The development adds another twist to the political crisis in the state months after the Rivers Assembly passed the Local Government Amendment Bill into law.
While Fubara did not assent to the bill, the lawmakers led by Martin Amaewhule vetoed him.
The law empowered the Rivers State Assembly to extend the tenure of council chairpersons, their vice, and councillors where it is deemed impossible to hold elections before the end of their three-year tenure.
But a court nullified the amended law, prompting an appeal. The appeal court is set to deliver a ruling on the matter today, June 20, 2024.