The son of Kenya's main opposition leader Raila Odinga was found dead in his home near Nairobi, prompting a police investigation and minor unrest in the capital, police and media reports say.

Police said Fidel Castro Odinga, 41, who was seen by political observers as a potential successor to his father, returned home on Saturday night after an evening out drinking with friends and was found dead in his bed on Sunday.

"The death ... is being treated as unexplained. We are investigating his final movements. A forensic pathologist has been called in and a post-mortem will be conducted to establish the cause of death," a Kenyan detective said on condition he not be named.

Condolence messages were immediately sent to Raila Odinga by President Uhuru Kenyatta and Vice President William Ruto, Capital FM news said.

The hashtag #RIPFidelOdinga trended on Kenyan Twitter and President Kenyatta sent the following condolence message on Twitter: 

Odinga, a former prime minister, leads the opposition Coalition for Reforms and Democracy (CORD) and is an outspoken critic of Kenyatta's government.

Last month he spearheaded a challenge of controversial anti-terror laws, accusing Kenyatta of turning Kenya into a dictatorship.

The Standard's website said reports of Fidel Odinga's death spurred a small but violent protest around Nairobi's Kibera slum.

The newspaper said the protesters pelted motorists with stones and blocked the roads before being dispersed by police.

Source: Agencies