Abuja: An explosion hit the office of Nigeria's Independent National Electoral Commission (INEC) in the northern city of Suleja on the eve of parliamentary polls.

Bomb attacks were witnessed during the campaigns and a prominent militia group, Movement for the Emancipation of the Niger Delta (MEND) threatened to disrupt the voting process but later they withdrew the warning.

Election for the country's Senate and Lower House of Representatives was scheduled for April 2, but put off to April 9 due to issues of logistic.

It is the first in series of elections that would see the oil rich African country elect a President and 36 state governors.

Yushua Shuaib, spokesman for the country's National Emergency Management Agency said, "There was explosion with some casualties but the injured have been taken to a nearby hospital for treatment."

MEND which claims to be fighting for better resource control is based in the oil rich Niger Delta in the north, another group Boko Haram has been killing politicians after issuing its own threat earlier.

Boko Haram is an Islamic sect that wants to install Sharia rule in the country and on the process preaches against Western education.

Nigeria has tightened its internal security by closing its land border throughout the period of the elections which is the fourth since return to democracy in 1999.