Odinga's running mate Kalonzo and other Nasa leaders skip event.
Kenyan opposition leader Raila Odinga was on Tuesday 'sworn-in' as the 'people's president' in front of thousands of supporters at Nairobi's Uhuru Park.
"I Raila Amolo Odinga, in full realisation of the high calling, assume the office of the People's President of the Republic of Kenya," he said in an the oath administered by a Nairobi member of Parliament TJ Kajwang.
"We have accomplished our promise to Kenyans," Mr Odinga told his supporters.
The National Super Alliance (Nasa) co-principals including Odinga's running mate Kalonzo Musyoka, Musalia Mudavadi and Moses Wetang'ula skipped the mock inauguration which took less than 10 minutes.
Soon after the event, Mr Odinga changed his Twitter profile to "President of the Republic of Kenya".
Mr Odinga claims the 2017 election, as well as the 2007 and 2013 polls, were stolen from him.
Nasa boycotted the October 26 repeat poll after the Supreme Court nullified the August 8 presidential election citing illegalities and irregularities.
Mr Odinga has refused to accept President Uhuru Kenyatta's re-election with Nasa challenging his legitimacy.
Nasa has been establishing parallel government structures in protest of the Kenyatta's administration.
The Kenyan government had warned against the inauguration ceremony saying it was a treasonable act and on Tuesday switched off three major television and radio stations who were broadcasting the event live.
-Reporting by Beatrice Kangai and The EastAfrican reporter.