Nigeria's upcoming elections "will not happen in peace, even if that costs us our lives," the leader of Boko Haram has promised in its latest video.

The 15-minute film was reportedly released on Twitter, a first for the Islamist extremists, on Tuesday. In it, the group's leader, Abubakar Shekau, promised more violence, which has already been ramping up in the lead up to the country's Presidential elections on March 28.

The elections were originally due to take place on February 14, but were postponed due to security concerns in the north-east.

"Allah will not leave you to proceed with these elections even after us, because you are saying that authority is from people to people, which means that people should rule each other, but Allah says that the authority is only to him, only his rule is the one which applies on this land," Shekau said in his "message to the leaders of the disbelievers".

"We say that these elections that you are planning to do, will not happen in peace, even if that costs us our lives."

Shekau also mocked claims that Boko Haram is ill-equipped to fight, saying: "we forced your forces to flee from their bases and we freed our imprisoned brothers from the prisons that you oppressed them in, only praise be to Allah."

Over three million people are believed to have been displaced by Boko Haram, with about half of those having fled Nigeria to neighbouring countries.

The terrorist group has garnered support through its determination to eradicate Nigerian democracy and replace it with an Islamic state guided by sharia law. The latest statistics suggest that violence associated with the organisation resulted in the deaths of more than 6,000 civilians in 2014. Its deadliest attack to date occurred in January 2015, when up to 2,000 people were killed in Baga, Borno state.

Nigeria's national security advisor, Sambo Dasuki, has vowed to eradicate the Islamists by March 28. "All known Boko Haram camps will be taken out" by then, he told AFP last week. "They won't be there. They will be dismantled".

The two main contenders in the elections – current President Goodluck Jonathan and his rival Muhammadu Buhari – have both promised to prioritise the security situation if they are to win.

However, Boko Haram continue to wreak devastation in the north-eastern parts of Nigeria, and insurgents made their first attack on a village in neighbouring Chad on 13 February.

Yesterday, two suicide attacks in Borno and Yobe states killed at least 38 people. According to AFP, there were also several explosions and gunfire at a rally for Buhari's All Progressives Congress party Okrika, Rivers State, in the south of Nigeria. A policeman was killed and several others injured, local reports suggest. A journalist covering the event was also allegedly stabbed.

It is not yet known who was responsible for that attack.

Earlier this week, the commander of US Special Forces operations in Africa pledged to help African nations in the fight against Boko Haram.

Major General James Linder said the US would provide technology to help African partners communicate between mobile phones, radios and computers.