Burundi's second Vice-President Marina Barampama has been sacked only six months after being appointed.
President Pierre Nkurunziza said she had been dismissed because of her insubordination and irresponsibility.
Mrs Barampama was a supporter of Hussein Radjabu, the ousted chairman of the governing Forces for the Defence of Democracy (FDD) party.
Divisions in the FDD, formerly a rebel group that won elections in 2005, have prompted fears of renewed violence.
The elections were the culmination of a peace process intended to end 12 years of conflict between Hutu rebels and the Tutsi-dominated army.
A special congress of the FDD party held this week chose Jeremy Ngendakumana as the new chairman, replacing Mr Radjabu, who was accused of abuse of power.
Mr Radjabu, who refused to attend the party congress, has denied accusations against him.
Mrs Barampama was appointed after her predecessor Alice Nzomukunda resigned over corruption and human rights abuses which she said were hampering Burundi's progress.
She also accused Mr Radjabu of interfering with her work.
The BBC's Kazungu Lozy in Bujumbura says Mrs Barampama was very close to the ousted FDD chairman and was appointed amid sharp disagreements within the governing party.
It is expected that Mrs Nzomukunda will be reinstated as the second vice-president.
Since independence in 1961, Burundi has been plagued by tension between the dominant Tutsi minority and Hutu majority.
More than 300,000 people died in the war sparked in 1993 by the assassination of Burundi's first Hutu head of state and democratically elected president, Melchior Ndadaye.