KINSHASA, Congo - Congo's opposition leader, who was declared the loser of the country's election on Friday, rejected those results and insisted he was president, setting the stage for a dangerous confrontation in the volatile Central African nation.

In the hours after incumbent President Joseph Kabila was named the winner of last month's race, unease gripped Congo's capital, though the mass mobilization of opposition supporters that some observers had feared did not immediately occur.

Columns of smoke smudged the sky above opposition neighborhoods where angry young men burned tires, sporadic shots pierced the air, and police wearing helmets and shin guards patrolled the streets. Across town in parts of Kinshasa loyal to Kabila, women cheered from balconies and supporters staged small victory parades across the wide boulevards.

The 40-year-old Kabila won 48.9 percent of the vote, or about 8.8 million of the 18.1 million votes cast. The 78-year-old Etienne Tshisekedi came in second with 5.8 million votes, or 32.3 percent, according to the final tallies released by election commission chief Daniel Ngoy Mulunda.

Repeated delays in releasing the results caused mounting tension in this nation that straddles a territory as large as Western Europe.

According to the country's constitution, the results should have been published no later than Tuesday, when Kabila's five-year term expired. The government delayed the announcement first by 48 hours, then by another 24, and Friday's news conference started three hours late, while diplomats shuttled between the two sides in an effort to ensure peace.

"I reject these results, and in fact I see them as a provocation against our people. . . . It's scandalous and vulgar," the opposition leader said by telephone late Friday. "We have done our own calculations, and I received 54 percent. To Kabila's 26 percent. His term is finished. I am the president. It's me that got the votes of the people."

Tshisekedi said that he had asked his supporters to remain calm and has not yet given the order for them to flood the streets until he sees if diplomatic efforts led by the international community will change the situation.

His refusal to accept the results is a dangerous development in this enormous country, where Kabila controls the army, and Tshisekedi controls the street.