Kenya's government has banned opposition rallies and dismissed calls for new elections, days after voters rejected a new constitution.
The opposition has called for a fresh round of elections
Vice-President Moody Awori said demonstrations supporting calls for elections would be seen as a "threat to national security".
His warning follows Saturday's rally in the capital Nairobi celebrating the victory of the referendum "No" vote.
The opposition had said the draft gave too many powers to the president.
Mr Awori said in a statement that opposition calls for nationwide protests were "inappropriate".
He said the rejection of the constitutional reforms were not grounds for new elections.
"The government considers these calls for nationwide rallies inappropriate and a threat to national security," he said.
"Accordingly, the government will not allow the planned rallies and [citizens] are cautioned not to attend the meetings," he said.
Tens of thousands of people attended the opposition rally in Nairobi.
Correspondents say many Kenyans used the referendum to protest against what they see as President Mwai Kibaki's poor performance since he was elected three years ago.
The president, who had led the "Yes" campaign, dismissed his entire cabinet in the wake of the referendum defeat.
But he has refused to dissolve parliament, saying the referendum was not a no-confidence vote.
Some campaigning during the referendum was marred by violence.
But by banning such expressions of dissatisfaction, the BBC's Adam Mynott in Nairobi says the fear is that Mr Kibaki will further alienate large sections of the population.