Around 650 people have been killed and 250,000 displaced in violence since last month’s re-election.
Many of the deaths occurred in ethnic clashes involving machete-wielding youths, although police have also shot dead demonstrators in Nairobi and Kisumu in a largely successful bid to crush opposition rallies.
More violence is feared as the opposition has called for further “mass action” on Thursday.
“Mass action only provides an opportunity for criminals to loot and commit other crimes,” State Internal Security Minister George Saitoti said.
“No freedom is absolute ... A few people will not be allowed to continue causing disruption,” he added.
Orange Democratic Movement leader Raila Odinga returned to the opposition stronghold of Kisumu, for the first time since the election, to a rapturous welcome.
“I’m saddened by the brutal killing of innocent, unarmed people demonstrating peacefully,” he said as thousands sang his name and six coffins of people said to be shot by police were laid out in a stadium.
“Kibaki has proved he has no respect for democracy.”
Most foreign and local observers say the poll was flawed, but the government says the opposition pre-planned mob violence against members of Mr Kibaki’s Kikuyu tribe.
The crisis has damaged Kenya’s economy, cut off supplies to neighbours, and tainted Mr Kibaki’s reputation as the man who democratised Kenya after the 24-year rule of President Daniel arap Moi.
An African Union spokesman, Assane Ba, said the AU “deplored violence in Kenya and appealed to the leadership to restrain their followers to stop any more killings.”
In an increasingly militant reaction to criticism from abroad, Foreign Minister Moses Wetangula summoned Britain’s High Commissioner Adam Wood to express displeasure.
Officials are irate at comments by Meg Munn, parliamentary undersecretary of state for the Foreign Office, that Britain has “not recognised” the Kibaki government.
“Our elections don’t need a stamp of authority from the House of Commons,” Wetangula told reporters.
The opposition has called for a boycott of companies owned by Kibaki allies, including Equity Bank, Brookside Dairies and bus companies CityHoppa and Kenya Bus.
“Sabotage of companies [is] illegal,” the government said.