Kenya's police chief announced a ban on fresh opposition demonstrations called for Monday, after protests last week degenerated into riots.
"We will not allow violent demonstrations," Inspector General of Police Japhet Koome told reporters on Sunday.
"The demonstrations they plan tomorrow (Monday) are illegal and will not be allowed," he said, adding that his force was ready to keep the peace and would arrest anyone carrying offensive weapons.
But veteran opposition leader Raila Odinga, who has called for people to take to the streets on Monday and Thursday against President William Ruto over the high cost of living, remained defiant.
"I am asking our supporters and all Kenyans to come out and join the peaceful demonstrations," he said at a church service on Sunday.
"I want to tell Mr Ruto and the IG Koome that we are not going to be intimidated," he said. "We are not going to fear tear gas and police."
Last Monday's demonstrations -- which were also not authorised by police -- descended into violence, with riot police firing tear gas and water cannon at people hurling rocks and setting tyres ablaze.
A university student was killed by police fire while 31 officers were injured in running battles in Nairobi and opposition strongholds in western Kenya, according to police.
More than 200 people were arrested, including several senior opposition politicians, while Odinga's own convoy was hit with tear gas and water cannon.
"You all saw what happened last week and we won't allow that to happen again, where hooligans come to town to loot and destroy people's property and businesses," Koome said.
It was the first major political violence since Ruto took office six months ago after beating Odinga in an election his rival claims was "stolen".
Many Kenyans are struggling to put food on the table, battling high prices for basic goods, a plunging local currency and a record drought that has left millions hungry.
Ruto, who is leaving the country on Sunday for a trip to Germany and Belgium, has already called on the opposition leader to halt the action.
"I am telling Raila Odinga that if he has a problem with me, he should face me and stop terrorising the country," Ruto said on Thursday.
Last week's protests proved costly -- Nairobi lost more than half its daily revenue as people kept away from the central business district, the city's governor Johnson Sakaja said.
Deputy President Rigathi Gachagua said the demonstrations cost the country $15 million.
During the election campaign, Ruto sought to portray himself as the champion of the downtrodden and vowed to improve the lot of ordinary Kenyan or so-called "hustlers".
But he has since removed subsidies for fuel and maize flour -- a dietary staple.
And last week, Kenya's energy regulatory body announced a hike in electricity prices from April 1, despite Ruto insisting in January there would be no such increase.