Kenyan police fired tear gas at protesters who took to the streets in defiance of a government warning after earlier demonstrations turned violent with more than a dozen people killed.

The opposition has vowed to stage three straight days of protests against President William Ruto's government, alarming the international community which has joined calls for a political solution to the crisis.

Schools and shops were closed in Nairobi and other cities, while Kenyans urged the two sides to bridge the impasse.

Police fired tear gas at scattered groups of demonstrators in Nairobi's Kibera slum, an Odinga stronghold, while offices in the capital's business district were largely shuttered.

It is the third time this month that opposition leader Raila Odinga has staged mass rallies against a government he says is illegitimate and to blame for a cost-of-living crisis.

In previous rallies, police used not just tear gas but live rounds to disperse stone-throwing protesters, drawing accusations of heavy-handedness from civil groups.

On the eve of Wednesday's demonstration, police described the protests as a "threat to national security" and the government declared it would not allow lawlessness to go unchecked.

"Anyone planning to unleash violence on Kenyans is hereby warned to cease and desist," said Interior Minister Kithure Kindiki.

Kindiki added that all available security resources had been deployed to maintain order.