Democratic Republic of Congo (DRC) opposition candidate Felix Tshisekedi has been declared by election officials as the provisional winner of a contentious December 30 presidential poll, various media reported on Thursday.

"Having gained… 38.57 percent of the vote, Felix Tshisekedi is provisionally declared the elected president of the Democratic Republic of Congo,” news agency AFP quoted Corneille Nangaa, the head of the Independent National Election Commission (CENI), as saying.

Tshisekedi beat off candidates including Emmanuel Ramazani Shadary, handpicked by incumbent President Joseph Kabila as his preferred successor.

He is the son of Étienne Tshisekedi, a long time DRC opposition politician who died in 2017.

The elections had been long delayed as Kabila repeatedly refused to step down after 18-years in power and despite his official term ending in 2016 after his two-term constitutional limit was up.

Kabila has been president since taking over his father Laurent Kabila who was assassinated in 2001. He was elected on his own right in 2006 and won a second term in 2011.

Kabila's refusal to step down sparked mass protests, with scores of people killed as DRC security forces cracked down on opponents.

Earlier this month, authorities clamped down on media and communications as tensions rose during vote counting after the polls, held amid allegations of vote-rigging.

The provisional results could still be challenged.