Since independence from Britain in 1960, Nigeria has known only one reasonably successful election, in 1979, when Shehu Shagari, a little-known northern politician, defeated the veteran southerner Obafemi Awolowo.
The African contingent is expected to be bolstered to 7, 900, including 2, 200 troops promised by Chad, AP news agency quotes a Nigerian military official, Col Shehu Usman Abdulkadir, as saying.
In July and August 2012 suicide bombers tried but failed to kill the shehu - or traditional ruler - of the Borno emirate in north-east Nigeria as well as the emir of Fika in Yobe state.