A security source said the men were believed to be trying to assemble an explosive device when it went off, killing at least two of them in a building situated close to a residential neighbourhood for members of local government.
“Emergency response agencies have already moved to the scene and have cordoned off the area to protect life and property,” said Yushua Shuaib of the National Emergency Management Agency.
Angry youths launched violent protests in northern cities this week after President Goodluck Jonathan, a Christian from the south, was declared the winner of elections last Saturday, defeating ex-army ruler and northern Muslim Muhammadu Buhari.
Churches, mosques and homes were set ablaze in the worst unrest for years as Buhari supporters rejected the outcome.
There are fears of further violence ahead of governorship and state assembly votes in Nigeria’s 36 states next week.
Shehu Sani, president of Nigeria’s Civil Rights Congress, said he believed as many as 260 people had been killed across the north, with the heaviest toll in Kaduna.
A curfew and heavy military presence has largely brought the violence under control, but it is feared the death toll could be much higher with fighting raging in towns including Zonkwa and Kafanchan, southeast of Kaduna, before the army arrived.
The presidential election was judged by domestic and foreign observers to have been the most credible for decades in Africa’s most populous nation, but Buhari insists that foul play in some areas deprived him of what could have been a victory.
Nigeria holds governorship and state assembly votes in most of its 36 states on Tuesday.
The vote in Kaduna and the nearby state of Bauchi has been postponed by two days to allow the security situation to stabilise, but with attacks on electoral offices, members of the National Youth Corps who are helping run the polls, and police stations, many fear security will be far from guaranteed.