Opposition presidential candidate Muhammadu Buhari, of the All Progressives Congress, speaks during the Nigeria Labor Congress in Abuja, Feb. 9, 2015. Reuters

Nigerian presidential candidate Muhammadu Buhari drew thousands of supporters Monday to a campaign rally in Borno state, a stronghold of Boko Haram insurgents, where he pledged to wipe out the militant group. Buhari, from the All Progressives Congress political party, packed popular Ramat Square in Maiduguri, and was joined by Borno Gov. Kashim Shettima and other party leaders from across the country, according to local media reports.

“If elected, I will focus on tackling the persistent insecurity affecting the northeast,” Buhari, 72, promised. “It’s not easy, as the damage has been done.” He continued: “Boko Haram’s ideology contradicts Islamic principles because [Islam] does not allow the senseless killing of innocents. It is unfortunate that innocent people are being killed in mosques, churches and their homes."

The Borno state government declared Monday a public holiday to encourage people to attend the rally. Nigeria had been scheduled to hold its elections on Saturday, but the contest was delayed amid military leaders' concerns that Boko Haram insurgents will not allow for a safe election process. The country’s official electoral commission has since postponed the vote to March 28.

Buhari, a former military ruler, is among 13 challengers running against President Goodluck Jonathan. He is considered the most viable rival against Jonathan’s People’s Democratic Party, which has ruled the country since its return to democracy in 1999. He is running for president for the fourth time since 2003.

Boko Haram has threatened security in Nigeria for years. It has declared a self-styled “Islamic caliphate” and targeted neighboring African nations in recent months. “If an APC government is elected, all towns under Boko Haram’s control will be liberated and rebuilt,” Buhari said.

Buhari canceled an earlier visit to Borno because of security concerns. He is popular in the area partly because he is a northern-born Muslim, according to Agence France-Presse. Jonathan is from Nigeria's mainly Christian south. He visited Borno in January.