Margaret Hill, the daughter of oil worker Mike Hill, was snatched as she travelled to school by car in Port Harcourt, in the south of the country. Kidnappers smashed a window as the car sat in heavy morning traffic and grabbed the toddler, according to an official at the British High Commission.

Reports since have suggested the kidnappers are in contact with Margaret's father, who has lived in Nigeria for 10 years. Mr Hill, originally from Murton in Co Durham, is believed to be working for Nigerian-based drilling firm Lonestar.

The Foreign Office called for the "immediate safe release" of the girl, whose mother is a Nigerian national.

"We do not know who took her. We are in contact with her parents and are providing assistance," a spokeswoman said. "High Commission officials are in contact with the Nigerian authorities. We call for her immediate safe release."

The British High Commission said it was unclear who was behind the kidnapping, but added that criminal gangs were usually to blame.

A spokesman said: "We are in contact with her parents and we are providing assistance to them. High Commission officials are in contact with the Nigerian authorities at federal and state levels and we are calling for her immediate release."

Despite Nigeria being Africa's leading oil exporter, more than half - 60% - of the country's population still live below the poverty line.

Kidnappings have become an almost weekly occurrence in the south of the country, where many foreign oil workers are based. More than a dozen foreigners are currently in captivity and more than 200 have been taken since the end of 2005.

Hostages are generally released unharmed after a ransom is paid - often by governments that control huge, unregulated security slush funds. But despite the increasing kidnappings, the targeting of women and children is uncommon, with attackers generally focusing on male employees of large oil companies.