Protesters in the Kenyan city of Kisumu say police are shooting at them and using tear gas amid anger over election results in the stronghold of opposition leader Raila Odinga.
Sebastian Omolo said that chaos broke out as soon as Mr Odinga finished speaking on television.
Mr Odinga says hackers infiltrated the database of the country's election commission and manipulated Tuesday's voting results in what he calls an "attack on our democracy".
Results show President Uhuru Kenyatta with a wide lead after votes from the vast majority of polling stations were counted.
Kisumu shopkeeper Festus Odhiambo says he is praying for peace even as roads into the city's slums have been blocked by bonfires and boulders.
The city has been a flashpoint in past elections.
Meanwhile, the chairman of Kenya's election commission says allegations by Mr Odinga that the commission's database was hacked in order to manipulate results will be investigated.
Chairman Wafula Chebukati said that an audit is likely to be ordered to address concerns about the system used for Tuesday's elections.
"For now, I cannot say whether or not the system has been hacked," Mr Chebukati says.