A Belarusian woman kidnapped in Nigeria's oil-rich south 11 days ago was released early Thursday, but has serious injuries, private security contractors said.
The woman was being treated for injuries, including bullet wounds and a fracture, and may require surgery, one of the contractors said, requesting anonymity due to restrictions on speaking to the media.
It was not immediately clear how or when the woman sustained the injuries.
The woman, a mother of four, had been working for a catering company that provides food to oil companies when gunmen seized her and her driver outside her home. The driver was released within a few hours.
Militant groups have kidnapped around 100 foreigners since the beginning of the year in the southern Niger Delta region, the heart of production in Africa's largest oil exporter. Some groups demand political reforms, such as a greater share of oil revenues, while others seek cash ransoms.
Hostages are usually released unharmed, but there have been a handful killed in crossfire between the Nigerian military forces and their captors. Women have not usually been targets, but two foreign women as well as three Nigerian women have apparently been seized so far this year, and gunmen snatched a Nigerian toddler from an affluent suburb of Port Harcourt on Wednesday.
Most oil corporations and their service companies have required their foreign employees to evacuate their families. But some, like the Belarusian woman, are married to Nigerians.
Analysts say instability has grown in the last month, after Nigeria's ruling party announced a landslide win in elections that international and domestic observers said were severely flawed by rigging and violence.
Militant groups have said the government's announced victory undermines its promise to improve the lives of the region's inhabitants, most of whom have no access to clean water or electricity, despite living on top of hundreds of billions of dollars worth of crude.
A string of protests and militant attacks have cut the 3-million-barrels-per-day production capacity in the country by about a third.
Nigeria is rated as one of the most corrupt countries in the world by Berlin-based watchdog Transparency International.