Democratic Republic of Congo President Joseph Kabila is due to be sworn in for a new term, as opposition leader Etienne Tshisekedi continues to assert that he is instead the country's rightful leader.

The inauguration Tuesday follows an election last month that international observers said had numerous irregularities during the voting and the counting process.

Mr. Kabila has said there is no question about the legitimacy of his re-election, and election officials say he easily won the vote.

But Tshisekedi has rejected the results as fraudulent and declared himself president, saying he will take office Friday.

The United States called the vote “seriously flawed,” although it was not clear if the problems were enough to change the outcome of the election.

Mr. Kabila has suggested Tshisekedi use the appeals system to challenge the results.

The presidential and legislative polls were only the second free elections in Congo since the nation was torn apart by several years of warfare that ended in 2003.