Gunmen in Nigeria's volatile southern Niger Delta abducted five Chinese workers in the early hours of Friday in what appeared to be a kidnapping for ransom, authorities and security sources said.
The Chinese embassy in Abuja said it was in contact with authorities in Rivers state, where the kidnapping took place, to try and secure the release of the men.
Abductions for ransom are common in the oil-producing delta.
"Five Chinese people were abducted at about 5 am on Friday morning. The details are not yet clear. The embassy is taking an active role in trying to rescue them," said the embassy's press secretary Zhang Hong Liang.
He said the embassy was not yet sure who had employed the men but it may have been a telecoms firm.
Energy-hungry China has been strengthening ties with Nigeria, offering investments and technical help with Nigerian infrastructure in return for good deals on oil drilling rights and supplies of crude.
A security expert working for a major oil company in the region said he had heard the five men had been working on a vandalised electricity line in the Emouhua area of Rivers state.
"They were abducted by community-based militants and have been taken to an unknown location," the source said.
This means the kidnappers 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 Italian oil company Agip 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 and many fear the violence will worsen in the build-up to Nigeria's general elections in April. 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.
Nigeria, the world's eighth-biggest exporter of crude oil, gets all its oil from the Niger Delta but residents of the impoverished wetlands region complain that they have been neglected by central and local governments.
Poverty and high unemployment fuel militancy and crime. The Nigerian security forces are unable to control the remote waterways of the delta where kidnappings, attacks on oil facilities and theft of crude oil are commonplace.
The MEND, which says it wants greater local control of oil assets and compensation from companies for oil spills, launched a series of attacks last February that forced the closure of a fifth of Nigeria's oil output capacity.
The faceless group has said it did not want money for the four Agip workers it is currently holding captive but would release them in exchange for four prisoners of Niger Delta origin held in Nigerian jails.
As well as politically motivated campaigns by groups like the MEND, attacks and abductions by local youths embittered by the lack of prospects and infrastructure are common.