South Africa says two of its citizens were abducted this week in Nigeria's volatile, oil-rich Niger Delta region.

The South African Foreign Affairs Ministry says its officials in Nigeria are doing everything they can to secure the hostages' release.

It says the victims were kidnapped Tuesday. It is not clear who carried out the abduction.

Gunmen in the Niger Delta regularly attack oil company facilities and kidnap their staff. Most hostages are released unharmed.

Some attackers are militants who say they are fighting so the region's impoverished residents get a greater share of the oil wealth. Others are gangs motivated by the ransom companies pay for the hostages.

A surge in the unrest that began in late 2005 has resulted in Nigeria's oil production dropping by about 25 percent.

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