But Zhang said the embassy was not sure yet who the men were employed by but it may have been a telecoms firm.
The security source said the kidnappers were "community-based militants", which means they were likely to be armed youths from the local area seeking a ransom rather than members of an organised militia pressing political demands.
Three Italians and one Lebanese working for an Italian oil company have been held captive in a different part of the delta since December 7 after they were kidnapped by fighters from the Movement for the Emancipation of the Niger Delta (MEND).
Kidnappings have plagued the delta for many years but they intensified in 2006.
Almost all hostages in the delta are released unharmed after their employers and local authorities pay ransoms. However, one Briton and one Nigerian were killed last year in separate botched attempts by Nigerian troops to free them.