A presidential spokesman said a panel would be set up to review the contracts, which included appointments and licences "to determine their propriety and relevance".

Among the contracts affected are lucrative offshore oil concessions awarded to companies linked to powerful military interests in preceding governments.

The statement said decisions would be reconfirmed, adjusted or cancelled based on their relevance to current realities in the oil-producing West African country of 108 million people.

No further details were immediately available, but President Obasanjo pledged on his inauguration on Sunday to put the fight against corruption to the top of his agenda.

He said that the kind of corruption which has plagued Nigeria for decades would no longer be tolerated.

"Corruption will be tackled head on," he said.

"No society can achieve its full potential if it allows corruption to become the full-blown cancer it has in Nigeria."

EU lifts sanctions

Nigeria Correspondent Barnaby Phillips: A decisive measure in the fight against corruption

In a separate development, the European Union has announced it will lift all remaining sanctions against Nigeria and resume development aid from Tuesday, following the return to civilian rule.

The EU imposed the sanctions in 1995, following the execution of nine Ogoni activists.

Most were lifted when General Abdulsalami Abubakar took power and promised to restore democracy.

In a farewell speech on Friday, the outgoing military leader, General Abubakar, defended his government's record, but urged the army to resist any temptation to take power again in the future.

His last move, before handing over power, was to abolish the decree allowing detention without trial.

The Nigerian economy has been steadily withering after years of waste, corruption and mismanagement and unemployment is soaring.