Boko Haram has renewed its attack on Nigeria's leadership in a video posted online by calling on President Goodluck Jonathan to convert to Islam.

In footage posted on YouTube the sect's leader Abubakar Shekau insisted Boko Haram would not negotiate with the government.

"You should abandon this ungodly power, you should repent and forsake Christianity," he said.

Shekau denied Boko Haram had targeted women and children in its campaign of violence. It attacked "those who have offended us, arrested our people and killed them", he said.

He warned "imposter" groups who committed attacks in the name of Boko Haram that they would be hit.

He dismissed US claims that Boko Haram was a terrorist group and told Barack Obama: "You said I'm a global terrorist, then you are a terrorist in the next world."

The video clip has not been authenticated but is similar to previous Boko Haram online posts.

Jonathan hits back

Jonathan dismissed the tape, saying he would not bow down to blackmail.

His spokesman, Reuben Abati, said he would not resign or convert to Islam.

"When Nigerians voted overwhelmingly for President Jonathan in the 2011 general election, they knew they were voting for a Christian," he said.

"As president, Jonathan is the leader of both Muslims and Christians. It amounts to sheer blackmail for any individual or group to ask the president to convert to Islam," Abati added.

"The president cannot be intimidated by any group or individual. The president will never resign. Nobody should imagine that he will succumb to blackmail".

Boko Haram (which means "Western education is sin") came to prominence in 2009 after a week-long uprising and military assault that left 800 people dead.

It resurfaced in 2010 after claiming responsibility for a series of suicide bomb attacks and has since then continued its insurgency.