According the U.S. DEPARTMENT OF STATE:
http://www.state.gov/r/pa/ei/bgn/2836.htm#history
You are in: Under Secretary for Public Diplomacy and Public Affair..
ROFILE
OFFICIAL NAME:
Federal Republic of Nigeria
Government
Type: Federal republic.
Independence: October 1, 1960.
Constitution: The 1999 constitution (based largely on the 1979 constitution) was promulgated by decree on May 5, 1999 and came into force on May 29, 1999.
[...]
Independence
Nigeria was granted full independence in October 1960, as a federation of three regions (northern, western, and eastern) under a constitution that provided for a parliamentary form of government. Under the constitution, each of the three regions retained a substantial measure of self-government. The federal government was given exclusive powers in defense and security, foreign relations, and commercial and fiscal policies. In October 1963, Nigeria altered its relationship with the United Kingdom by proclaiming itself a federal republic and promulgating a new constitution. A fourth region (the midwest) was established that year. From the outset, Nigeria’s ethnic, regional, and religious tensions were magnified by the significant disparities in economic and educational development between the south and the north.
Why did you post about nigeria? We are talking about Kenya here.