Pfizer is accused by Nigeria of conducting an illegal drug trial

The government earlier withdrew the case - just as it was due to begin in the capital Abuja - to add new charges.

The government is seeking $7bn (£3.4bn) in damages from the US group.

It claims Pfizer conducted illegal trials of an anti-meningitis drug that killed and disabled children. Pfizer denies the allegations.

Pfizer has denied all wrongdoing and maintains that it had local and international approval for the drug trial, which it says helped to save lives.

But government lawyers have now filed a new lawsuit adding a number of additional charges to the original claims, which follows the recent discovery of new evidence.

This includes papers that suggest Pfizer committed fraud by not obtaining consent from the affected families as they were obliged to do under company rules, government lowers said.

They said the original suit made reference to a softer charge of "fraudulent representation".

Drug tests

The move came almost a month after the court rejected the government's request to amend its suit.

The Nigerian government has accused Pfizer of carrying out illegal trials of its Trovan antibiotic in 1996, which they say caused many deaths and severe mental and physical disabilities in many of the people it was given to.

It maintains its regulatory authorities had not approved the then-unregistered drug, which was tested in Nigeria's north-western Kano State at the height of a meningitis outbreak.

The Kano regional government is also mounting both civil and criminal cases against Pfizer, which has undertaken a major public relations offensive in the country to explain its position.