Kenyan protesters have clashed with club-carrying young men, believed to be loyal to the government, in the centre of the capital, Nairobi.

The demonstration, held in the wake of the death in custody 10 days ago of blogger and teacher Albert Ojwang, was called to demand the sacking of a top police officer.

Police initially said that Mr Ojwang died of self-inflicted wounds, but were forced to retract the statement after an autopsy found that it was likely he died after being assaulted. Two policemen have been arrested in connection with the death.

The protest comes amid simmering tension ahead of next week's first anniversary of the storming of parliament by demonstrators.

Earlier on Tuesday, there were pockets of violence in the capital's central business district when groups of young men riding motorbikes, armed with whips and clubs, attacked protesters.

Videos show the men - described locally as "goons" - seemingly working side-by-side with police, who fired teargas to try and disrupt the demonstrations.

The police have denied any link saying that it has "noted a group of goons armed with crude weapons, in today's protests... The service takes great exception and does not condone such unlawful groupings."

A vendor was shot during Tuesday's demonstration, sparking renewed outrage from Kenyans who accuse police of using excessive force against protesters.

Boniface Kariuki was reportedly selling masks when a uniformed police officer fired a bullet at close range, critically injuring him.

His father, John Kariuki, told local media that the bullet went through his head, just above the ear.

The 22-year-old vendor is now under medical observation after successful surgery, his father said.

In a statement, the police said it was aware of "an incident involving [the] shooting of an unarmed civilian by a police officer using an anti-riot shotgun". The policeman allegedly responsible has since been arrested, it added.

Officers had been deployed across key parts of the city, in an attempt to block protesters from accessing major intersections and government buildings.

Deputy police chief Eliud Lagat has stepped aside as an investigation into Mr Ojwang's death is under way.

But activists want him removed from office as it was his complaint against the blogger that led to the young man's arrest. The 31-year-old was accused of defaming Mr Lagat on social media.

"We shall not be intimidated. We shall remain unbowed. We want Lagat to step aside," one protester told the BBC.

"We want the guy to resign and we want the guy to be arrested. We want him to sit there and answer questions, you know. [He is] still on the payroll, still enjoying taxpayers' money," another said.

The situation in Nairobi remains tense. Most businesses in the city centre are shut and there are visibly fewer people than usual on the streets.

Last year's protests, led by young Kenyans, were against an unpopular finance bill which sought to introduce new taxes. It culminated in the protesters entering parliament on 25 June and forced the government to drop the controversial proposals.

There are no contentious tax measures this year, but activists plan to build up momentum to what they are calling "a total shutdown" of business next Wednesday.

Additional reporting by Akisa Wandera and Anthony Irungu