KINSHASA, Congo - Police fired tear gas Friday at supporters of Congo's opposition leader who had gathered near a stadium to see him inaugurating himself as president, three days after President Joseph Kabila was sworn in for a second term.

It was unclear if 79-year-old opposition leader Etienne Tshisekedi would make it to Kinshasa's Martyrs' Stadium for the unofficial act that observers fear could spark more election-related violence in the mineral-rich central African nation.

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

About 1,000 Tshisekedi supporters of gathered near the stadium Friday morning. Several tanks waited nearby. Police also thronged Tshisekedi's neighbourhood, possibly to keep him from reaching the stadium.

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 country's 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 per cent 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.

Tshisekedi last month ordered his followers to stage jailbreaks to free detained colleagues.

Observers fear unrest if Tshisekedi, who is enormously popular with the country's impoverished masses, orders his supporters to take to the streets.

The November election was only the second democratic vote in Congo's 51-year history, and the first to be organized by the Congolese government rather than by the international community.

Congo, which is sub-Saharan Africa's largest country, has suffered decades of dictatorship and civil war. The country's east is still wracked by violence perpetrated by dozens of militia and rebel groups.