A team of reporters saw the group of police officers force their way into a home in Kinshasa on Saturday. They dragged out a young man and threw him into the back of the waiting car.

The scene was repeated a few blocks later.

Human Rights Watch senior researcher Anneke Van Woudenberg says she is receiving calls from residents in neighborhoods throughout the city reporting abductions by security forces.

Congo's capital remained tense on Saturday. The country's opposition leader rejected the results and proclaimed himself president, setting the stage for confrontation. Reacting Friday to the election commission's announcement that Joseph Kabila had won the Nov. 28 election with 49 percent of the vote, veteran opposition leader Etienne Tshisekedi said: "I consider myself from this day on as the elected president."

Government spokesman and Communications Minister Lambert Mende said Saturday the statement was an "infraction of the law" and an "attack on the constitution."

"We must firmly condemn the self-declaration by Mr. Etienne Tshisekedi," he told a press conference. "It's an irresponsible act that violates the laws of the republic," he added. "The public prosecutor has the authority to take the matter to court."

The election commission said Tshisekedi had come second with 32 percent of the vote, but he claimed he had in fact won with 54 percent, saying his party had collected vote figures directly from polling stations.

UN Secretary-General Ban Ki-moon joined international appeals for calm in Congo. Ban noted the official results which "indicated" incumbent Kabila had won and "calls for any differences regarding the provisional results of the polls to be resolved peacefully through available legal and mediation mechanisms," said his spokesman Martin Nesirky in a statement released late Friday.

The UN secretary-general "strongly condemns any acts of violence in connection with the electoral process" and "reiterates his call for calm and urges all candidates and their supporters to exercise restraint and refrain from any acts of violence, provocation and incitement to violence," the statement added.