Nigeria's president Olusegun Obasanjo (File)

President Olusegun Obasanjo said in a statement Sunday he had placed Nigerian security forces on full alert before the forthcoming polls.

The elections are set to be a landmark in Nigeria's troubled history, marking the country's first transfer of power from one elected civilian leader to another.

President Obasanjo said security forces would "clamp down heavily" on anyone who threatens to disrupt the country's polls.

President Obasanjo said he had taken the step to prevent any threat to, what he described as Nigeria's "collective desire for trouble-free elections."

The President's statement is to be aired on national television as part of a special Easter broadcast.

Elections for 38 state governors are to take place on Saturday, with presidential polls to follow a week later.

Last week, a report by US-based Human Rights Watch criticized the Nigerian government for failing to tackle political violence before the polls.

EU election observers have said they will not be sending representatives to the restive Niger Delta in southern Nigeria, because of security fears.