Nigeria has reacted furiously to reports that the US has posted a $2m bounty for the capture of Liberia's exiled former leader, Charles Taylor.
Liberia's former leader lives in exile in Nigeria
A Nigerian spokesman said the US offer verged on state-sponsored terrorism and they would resist any attempts to seize Mr Taylor.
He went into exile in Nigeria as part of a plan to end Liberia's civil war.
The Bush administration says Mr Taylor should face trial at a special war crimes court in Sierra Leone.
Many assumed that once Mr Taylor was taken out of Liberia the Americans would leave the matter there.
But a small clause in a bill signed into law this week by President George W Bush suggests they have not forgotten him.
'Stone age' attitude
The bill in question provides funds totalling $87.5bn for operations in Iraq and Afghanistan.
But a small part of that budget refers to the provision of $2m reward money for the capture of what it describes as an indictee of the Sierra Leone war crimes tribunal - a clear reference to Mr Taylor.
Nigerian presidential spokesman Femi Fane Kayode said they were surprised and shocked by news of the bounty on Mr Taylor's head, a reward that encouraged lawless and illegal behaviour.
"Such a venture violates not only international law but also all the norms of civilised behaviour," he told the BBC World Service's Newshour programme.
Nigeria would resist any attempt to capture Mr Taylor, the spokesman said, adding that Liberia's ex-leader was under the protection of the Nigerian Government.
Mr Taylor's presence on Nigerian soil was the result of a plan agreed by African nations to resolve the conflict in Liberia, he added.
The decision by the US Congress to draw up a bill encouraging and endorsing people to go to another country to capture someone illegally was a "step back to the stone ages, " Mr Kayode said.
"In fact, this is a little bit close to what many of us would describe as state-sponsored terrorism."
Security has been increased around Mr Taylor's compound in Calabar, in the far south-east of the country, following reports of the US bounty.
The ex-leader has been there since August when he arrived with around 100 other people, although many have now left. According to a Liberian official close to Mr Taylor, this is partly for security reasons and partly because they found life there rather dull.
Mr Taylor was indicted by the war crimes court in Sierra Leone while he was still Liberia's president.
SIERRA LEONE SPECIAL COURT
Established by UN and Sierra Leone
Try those most to blame for war crimes
Mandate till 2005
Local and international prosecutors, judges
Funded by UK, US and others
It is seeking to try him on charges that he armed and trained Sierra Leone's rebels who waged a campaign of rape and dismemberment during the country's civil war.
As a former warlord, he was also involved in the bloodshed in his own country.
Under the terms of his asylum, Mr Taylor was warned not to communicate with anyone involved in political, illegal or government activities in Liberia.
However, the United Nations has warned that he is still meddling in Liberia's affairs from afar.
The UN's chief representative in Liberia, Jacques Klein, told the BBC he was surprised but delighted by news of the bounty.
The reward was unlikely to result in mercenaries going after Mr Taylor, Mr Klein said; the bounty's value was more symbolic.
"It's a signal to the African people that your lives are worth something. That we will no longer let regional dictators and criminals brutalise you, murder you, exploit you, and steal the state treasury."
At some point Mr Taylor would outlive his welcome in Nigeria and violate the terms of his asylum, Mr Klein said.
"They'll eventually probably throw him out and at that point the warrant is valid and the reward is valid."