The Nigerian federal government has filed criminal charges against US drugmaker Pfizer alleging improper behavior in a 1996 drug trial in the northern state of Kano in which it says 11 children died.

The federal government was already seeking $6.5 billion in a separate civil case. The government of Kano state is also seeking $2 billion in damages from Pfizer and has filed separate criminal charges too.

The criminal charges by the federal authorities were filed in May but this was not made public at the time. The case was due to come up for the first time in court yesterday, but was adjourned to October 29 in the absence of any representatives of the defendants.