Two politicians prevented from leaving the country hours after a court ordered their travel documents to be returned.
Kenya's main opposition leader Raila Odinga sworn himself in as "the people's president' on Tuesday.
Earlier on Tuesday, riot police sealed off an area where the opposition planned a rival gathering and teargassed people trying to approach it.
Kenya’s Supreme Court on Monday unanimously upheld the re-election of President Uhuru Kenyatta
At least 49 people have died since the first presidential election of August 8, which was later overturned, prompting Kenya's worst political crisis in a decade.
Kenya’s repeat presidential election, boycotted this week by millions, has reignited long-running tensions.
The first election, in August, was annulled by the courts because of procedural irregularities.
Odinga’s exit from the democratic process means opposition supporters’ faith in the system is at the point of collapse.
Odinga has another chance.