The U.S. Department of State warned American citizens Wednesday about the dangers of traveling to and within Nigeria during the country’s 2015 elections next month. The controversial elections were postponed for six weeks because of security concerns in Nigeria’s northeast region, which is a hotbed for the Boko Haram terror group.

“The Department of State alerts U.S. citizens of the risks of travel to Nigeria and urges caution while traveling within Nigeria during the general and gubernatorial elections on March 28 and April 11, 2015,” said the travel alert, which expires May 25.

Nigerian officials have urged voters against violence following the announcement of the election results. Post-election violence in Nigeria’s last presidential race in 2011 killed more than 800 people. The violence erupted with widespread protests in 12 northern states, according to international watchdog group Human Rights Watch.

“The 2015 elections again present a possibility of violence. U.S. citizens are encouraged to exercise caution during the election process, particularly in and around polling locations in the weeks before and after the elections,” the U.S. Department of State travel alert said Wednesday. “There is presently no reason to believe that U.S. citizens would be specifically targeted in the event of election-related violence."

The presidential election is hotly contested in the African nation. Nigeria’s President Goodluck Jonathan is running for a second term against primary challenger Muhammadu Buhari, a former military dictator. The election postponement prompted suspicion from Jonathan’s critics of ballot rigging. The ruling PDP party has remained in office since 1999, often through blatant voter intimidation, vote rigging and other illegal practices, according to BBC News.

The upcoming elections were originally scheduled for Feb. 14 and Feb. 28 but were delayed after Nigerian security forces fighting Boko Haram said it could not guarantee voters’ safety around the country, the Associated Press reported. The extremists hold a large swath of the country’s northeast, where the group is trying to establish a state based on strict Islamic law.

U.S. officials also previously recommended Americans to avoid all but essential travel to Nigeria’s northern states of Adamawa, Bauchi, Bayelsa, Borno, Delta, Gombe, Jigawa, Kaduna, Kano, Katsina, Kebbi, Niger, Plateau, Rivers, Sokoto, Yobe, and Zamfara, due to risk of kidnappings, robberies and other armed attacks by Boko Haram, whose members have targeted churches, schools, mosques, government installations, educational institutions and entertainment venues.

Since 2009, more than 11,000 people have died at the hands of Boko Haram militants, who have sworn loyalty to the Islamic State in Iraq and Syria. The violence has also displaced hundreds of thousands of Nigerians, according to the Nigeria Social Violence Project.