Switzerland has given the green light for the return to Nigeria of $290 million (SFr360 million) in funds seized in accounts linked to the late dictator, Sani Abacha.
This is part of the sum that Abacha plundered from the West African country and deposited in Swiss banks between 1993 and the time of his death in 1998.
"The transfer became possible following the signing of an agreement with the World Bank to monitor Nigeria's use of the funds," said Livio Zanolari, spokesman for the Swiss justice ministry.
The $290 million is to be paid immediately.
A second installment of $170 million will be made when assets have been converted to cash, said Zanolari, adding that he did not know how long this would take.
The money has been frozen in Swiss bank accounts since 1999. The Swiss Federal Court gave the all-clear for its return in February when it rejected an appeal by the Abacha family.
The Swiss government had sought World Bank involvement in a bid to guarantee that the money will go towards development projects in areas such as health, education and infrastructure, as promised by Nigeria.
The agreement with the World Bank has now been signed, said Zanolari.
Nigerian President Olusegun Obasanjo accused Switzerland in May of stalling on the return of the funds, but Swiss officials said the delay was only because of the need to work out details with the World Bank.
The Nigerian government claims Abacha created a criminal organisation after his takeover in 1993 and plundered $2.2 billion from state funds until his death from an apparent heart attack in 1998.
After he died, Swiss officials blocked about $700 million in Swiss accounts linked to Abacha and his associates. About $216 million has so far been returned to Nigeria.
Nigeria has been pushing with some success for the return of Abacha's looted funds from other countries, including Britain, Luxembourg, Liechtenstein and Austria.
swissinfo with agencies
Between 1993 and 1998, Sani Abacha is said to have plundered more than $2.2 billion from the coffers of Nigeria.
About $700 million was frozen in Switzerland.
More than $200 million of that amount has since been returned to Nigeria.
Switzerland's Federal Court ruled in February that a further $458 million in frozen funds could be returned.