Nigeria's President Muhammadu Buhari on Tuesday warned there was no longer any hiding place for the corrupt, as he hailed British and Swiss support for the recovery of stolen public funds.
"Switzerland and Britain have been very helpful indeed in the recovery of our assets. But we must build on what we have started," he told both countries' ambassadors separately in Abuja.
"It is also important to send a signal to the elite that it is no longer business as usual," he said, according to a statement from his office.
Buhari has vowed to recover "mind-boggling" amounts of stolen oil money and bring those responsible to book, as part of a drive against corruption and to replenish depleted government coffers.
The arrest in London last week of the country's former oil minister Diezani Alison-Madueke on suspicion of bribery and money laundering has shocked Nigeria's political establishment.
She was one of five people arrested on Friday as part of a probe into international corruption dating back to 2013, when she was a serving minister under president Goodluck Jonathan.
Magistrates in London on Monday granted police permission to retain for six months £27,000 ($41,000/36,500 euros) in cash seized during her arrest.
Alison-Madueke -- the first woman to hold the post of oil minister and the rotating presidency of the global oil cartel OPEC -- has previously been accused of involvement in large-scale fraud.
She has repeatedly denied wrongdoing.
On her watch, it was alleged the state-run Nigerian National Petroleum Corporation (NNPC) failed to remit $20 billion in revenue to the central bank.
Nigerian authorities had received "much help" from Britain, Switzerland and other nations to track down stolen public funds "by officials of past administrations", Buhari said.
But he called for "the processes of investigation, prosecution and repatriation of Nigerian funds stolen by corrupt public officials and their accomplices" to be speeded up.
Switzerland in March said it would return about $380 million linked to Nigeria's former military ruler Sani Abacha that was placed in several overseas accounts controlled by his family.
Some $500 million in Swiss bank accounts had already been returned.
Abacha, in power from 1993 until his death in 1998, is suspected of having siphoned off $2.2 billion from Nigeria's central bank in what the United States has called "brazen acts of kleptocracy".