Delta state police spokesperson Charles Muka says the kidnapping happened on Friday morning outside of a bank in Warri, the state capital.
Muka said investigators believe the man had been followed by kidnappers before the attack.
Muka said the kidnappers are asking for a $333 000 ransom.
A spokesperson with the US embassy in Nigeria declined to immediately comment.
Kidnapping in the Niger Delta remain common, with criminal gangs and militants often seizing expatriate oil workers.
Muka said he did not know if the man kidnapped Friday worked for an oil company.- SAPA