Yoweri Museveni has "badly rigged" Uganda elections that took place on Thursday, whose results are yet to be announced, Anyang' Nyong'o has said.
The Kisumu Senator said the tally so far by the country's electoral commission does not reflect the people's will.
"Evidence of stuffed ballot boxes is rampant. The state to curtail information on the rigging, and delays in opening up polling stations denied millions of voters access to ballot boxes," he said.
Nyong'o added that Ugandan security forces were ready to crash protests by people opposed to the manner in which the process is being carried out.
"Ugandans have resolved to resist the illegal and illegitimate stay in office by Museveni and the National Resistance Movement regime," he said in a statement on Friday.
The Senator called for solidarity by world democratic forces and asked them to resist temptation to lend credibility to "this shameful abuse of human rights by the Museveni government".
"Let international observers take note that it is the truth that Ugandans expect from them not artificial and hypocritical cleansing of this gross abuse of the democratic process."
Police on Friday Uganda's main opposition candidate Kizza Besigye and fired tear gas at his supporters as from the presidential election showed President Yoweri Museveni set to extend his 30-year grip on power.
While Museveni has presided over notable economic growth, critics - especially the young - accused him of not tackling corruption or creating jobs and of acting increasingly like an autocrat, and forecast the vote would be rigged.
