Police said they arrested 143 people in central London on Saturday after a demonstration against the re-election of President Joseph Kabila in the Democratic Republic of Congo turned violent.

Most of the arrests came at around 2100 GMT after a group broke away from the main protest in Trafalgar Square and began to damage property including cars and shops, Metropolitan police said. Members of the public were also threatened.

The anti-Kabila demonstration had started in Whitehall during the morning after agreement with police for a static protest, a police spokesman said.

All demonstrators have now dispersed, he added.

Brussels police arrested about 200 people on Friday night after similar violent demonstrations in the Belgian capital.

Etienne Tshisekedi, the main challenger to Kabila, declared himself president on Friday and poured scorn on provisional official results handing victory to the incumbent.

The U.S.-based Carter Center observer mission that monitored the election said the results issued by Congo's election commission lacked credibility.

(Reporting by Stefano Ambrogi)