Kenyan President William Ruto vowed on Friday that protests planned next week would not be allowed following two rounds of demonstrations that have left at least 15 people dead.
Opposition leader Raila Odinga's party called earlier in the day for three more days of protests from next Wednesday against tax hikes that Ruto signed into law last month.
Ruto beat Odinga in last August's election. He pledged to be a champion for the poor, but his critics say the tax rises will hurt Kenyans already struggling to afford basic commodities such as maize flour.
"Elections ended August 9 last year. You cannot look for the leadership of this country using the blood of the citizens, the death of the citizens and the destruction of property," Ruto said at the opening of a road in the town of Naivasha.
"These demos will not happen. Listen to me carefully: you cannot use extrajudicial, extra-constitutional means to look for power in Kenya."
The most recent demonstrations took place despite bans by the police, and Ruto did not say how he planned to stop the upcoming protests.
A spokesman for the U.N. Human Rights Office (OHCHR), Jeremy Laurence, said on Friday it was "very concerned by the widespread violence, and allegations of unnecessary or disproportionate use of force, including the use of firearms, by police during protests in Kenya".
Kenyan authorities have blamed the deaths on the protesters, some of whom have thrown rocks at police and vandalised public property. More than 300 people were arrested in connection with Wednesday's protests.
