KINSHASA, Congo - Congo's opposition leader held a private ceremony inaugurating himself president Friday after police prevented him and his supporters from gathering publicly, a spokesman said, a move that comes three days after President Joseph Kabila was sworn in for a second term.

Police fired tear gas at supporters of Etienne Tshisekedi as they tried to reach Kinshasa's Martyrs' Stadium. Police also gathered near the home of Tshisekedi, 79, prompting him to hold the ceremony Friday afternoon in the company of about a dozen colleagues, said party spokesman Jean Marie Vianey Kabukanyi.

Kabila was sworn in earlier in the week after he was announced the official winner of the November poll. Observers fear that Tshisekedi's move could spark more election-related violence in the mineral-rich central African nation. Police inspector general Charles Bisengimana said the situation was calm in Kinshasa on Friday.

Government spokesman Lambert Mende said the ceremony was a "non-event."

"It's an extremely regrettable act," he said, adding that officials were "saddened" that Tshisekedi "was expressing his frustration over his defeat in this fashion."

Tshisekedi earlier declared himself the winner of the election that international and local observers say lacked credibility, defying Kabila, who results said had 49 percent of the vote, compared with 32 percent for Tshisekedi.

Kabila came to power after his father's assassination and has led Congo for a decade. His father, Laurent Kabila, was a rebel leader who toppled the dictator of 32 years, Mobutu Sese Seko, in 1997.

Joseph Kabila was declared the winner following constitutional reforms he pushed through parliament limiting the election to one round. Under the old rules, any winner had to have more than 50 percent of votes.

Human Rights Watch said Wednesday that security forces have killed at least 24 people and detained dozens in attacks to quell dissent over the much-criticized vote.