By Alex Last
BBC News, Lagos
Former Nigerian Finance Minister Ngozi Okonjo-Iweala has been removed from her post as head of the country's economic reform team, officials say.
Okonjo-Iweala was credited with securing debt relief
Mrs Okonjo-Iweala, who negotiated the cancellation of $30bn debt to the Paris Club, was switched in June from the Finance Ministry to Foreign Affairs.
She had remained head of the economics team, but has now been replaced by the new Finance Minister, Nenadi Usman.
There has been no official explanation for the move.
Mrs Okonjo-Iweala may still be Nigeria's foreign minister but that belies her apparent sudden fall from grace.
A former top World Bank executive, it was as Nigeria's finance minister and head of President Olusegun Obasanjo's economic reform team that she made her name at home and abroad.
She saved - rather than squandered - the government's profits from oil revenues.
Then she negotiated the largest debt relief deal in Africa, which saw Nigeria's $30bn debt to the Paris Club partly written off, saving the country $18bn.
But without warning in June, she was suddenly switched from being the minister of finance to the prestigious, but less powerful position of foreign minister.
Analysts were concerned but were reassured by the fact that she retained her post as head of the economic team. But now that has gone too.
Her successor, Nenadi Usman, has pledged to keep the reform programme going.
Some reports say President Obasanjo had decided that Mrs Usman had now settled into her new role and was ready to assume more of her duties.
But critics of the president say it appears the change is because of a personal clash.
The timing of the move has also raised eyebrows.
Mrs Okonjo-Iweala is currently in London, trying to secure further debt relief for Nigeria.
Although the country's economic reform programme is unlikely to change in the short term, the state of Nigeria's finances will now be under even greater scrutiny.