Chinese officials say unidentified attackers have kidnapped three Chinese workers in southern Nigeria.

A Foreign Ministry spokesman, Qin Gang, says the employees of the China Civil Construction Corporation were taken this week, near the company's compound in Calabar, the capital of Nigeria's Cross River state.

The spokesman says the Chinese Embassy in Nigeria is working to rescue the workers.

He did not say whether officials have been in contact with the abductors or whether any demands have been made.

Gangs and militants in Nigeria's oil-rich Niger Delta region have kidnapped dozens of foreign workers over the past two years.  Most have been released unharmed.

China has been increasing its presence in Africa in recent years, in an effort to secure more markets and materials for its booming economy.

Some information for this report was provided by AFP and Reuters.