Lagos , Nigeria ( CNN ) -- Concerned about ongoing violence , Nigerian election officials Thursday delayed gubernatorial elections in two states . Voters in Kaduna and Bauchi states will now go to the polls on April 28 , said Attahiru M. Jega , chairman of the Independent National Electoral Commission . Elections will continue April 26 in other states . `` This is to allow for further cooling of tempers and for the security situation in those states to improve , '' Jega said . The development came after Goodluck Jonathan , who was declared the winner in the recent presidential election , warned perpetrators of postelection violence that `` enough is enough . He said the unrest in a series of elections brings back memories of events leading up to a 1960s civil war in the nation . Jonathan , who ran as the incumbent , hails from the oil-rich southern region , which is majority Christian . Parts of the mostly Muslim north charged the elections were rigged . Armed protesters in the region prowled the streets chanting the name of former military ruler Muhammadu Buhari , the main opposition frontrunner . `` We are shocked by these horrific acts , which strike at the heart of our nation , '' Jonathan said in a statement Thursday . `` These acts of mayhem are sad reminders of the events which plunged our country into 30 months of an unfortunate civil war . '' Muslims fearing reprisal attacks in Christian areas have fled to military barracks or neighboring states , the Nigerian Red Cross said . More than 40,000 people are displaced in the north , according to the aid group . Government officials have declined to release the number of fatalities or injuries over fears it could prompt revenge attacks . Jonathan urged protesters to avoid violence , saying `` enough is enough . '' `` There are ... no grievances that our laws and courts can not address , '' he said . Jonathan 's warning comes two days after he pledged a `` new dawn '' for the nation following the vote hailed as a significant improvement from past polls . The last election four years ago was widely condemned for rampant vote rigging , violence , theft of ballot boxes and intimidation . While Saturday 's election was marred by violence , reports of underage voting and other logistical problems , observers considered it an improvement . Action Congress of Nigeria , an opposition party , Thursday called the presidential election `` the most systematically rigged election in Nigeria 's history '' and warned against a repeat in next week 's gubernatorial elections . ''President Jonathan should call his dogs of war at the PDP ( Peoples Democratic Party ) to order , so that they will not push their luck by attempting to thwart the will of the people any more than they have already done , with the grim consequences that we all can now see , '' the party said . World leaders have urged the west African nation to probe allegations of ballot stuffing and unusually high turnout in some areas . Nigeria is Africa 's largest oil producer and its most populous nation with 150 million people .
NEW : Electoral College stops voting in two states . The president tells protesters to avoid voting . ` ` There are ... no grievances that our laws and institutions can not handle , '' he says . Many in the mostly Muslim north charge the vote is rigged after Jonathan 's election .