A second officer has been arrested in connection with the death of a teacher in custody in the Kenyan capital Nairobi, the police watchdog said Friday, a case that has sparked nationwide outrage.

Albert Ojwang, 31, died in custody last weekend after being arrested for criticising a senior officer online.

Police initially said Ojwang had fatally injured himself by banging his head against a wall, but a government pathologist later found the wounds were "unlikely to be self-inflicted".

His death has reignited anger over a wave of abductions and heavy-handed policing during anti-government protests last year.