March 25, 2015/Bloomberg

Nigeria announced the closing of its land and sea borders at midnight Wednesday as its security forces prepare for presidential and legislative elections on March 28.

Borders will remain shut until midnight Saturday “to allow for the peaceful conduct of the forthcoming national elections,” the Interior Ministry said in a statement posted on an official government website.

The army is ready to ensure security during the elections and their aftermath, it said on its Twitter account. Analysts expect voting to be the closest since Africa’s most populous country emerged from military rule in 1999. President Goodluck Jonathan, 57, and his main rival, former military ruler Muhammadu Buhari, 72, were level on 42 percent support in a December poll by Afrobarometer.

Nigeria and neighboring countries including Chad, Niger and Cameroon, are battling the Islamist militant group Boko Haram, which has been fighting for the past six years to impose a strict version of Shariah, or Islamic law, on Africa’s biggest oil producer.

The elections were delayed for six weeks after Jonathan’s security adviser said the military couldn’t ensure a safe vote because of the fight against Boko Haram.

Voter accreditation is due to begin at 8 a.m. on March 28 and will be followed by balloting. Jonathan is seeking a second full term, while Buhari is attempting to win his first ballot after losing presidential elections in 2011, 2007 and 2003.

Two journalists working for Al-Jazeera television were put under house arrest in the northeastern city of Maiduguri, the military said on its Twitter account Wednesday.

They were “monitored by military intelligence operatives until they eventually had to be restrained to their hotel” after having been found “loitering around areas where military operations are ongoing,” it said.