The incident, days ahead of general elections, occurred after police earlier Tuesday discovered two homemade bombs in a car carrying three suspected Islamists believed to be heading for the same rally in the city of Maiduguri.
“Three suspected members of Boko Haram fired several shots from their AK-47 rifles from outside the venue, which caused panic and a stampede among party supporters attending the rally,” said assistant police commissioner Zakari Adamu.
“This resulted in the deaths of four people. The attackers slipped away before they could be arrested.”
Thousands of people were attending the rally for the All Nigerian Peoples Party, the ruling party in Borno state, where Maiduguri is the capital. No one was believed hit by the gunfire.
In the earlier incident when police discovered the bombs, the three suspected sect members ran. Authorities opened fire, killing one and wounding another, but the third escaped.
“From all indications the suspected Boko Haram members wanted to detonate the bombs at the campaign rally,” Adamu said.
The sect known as Boko Haram has been blamed for a series of attacks in Maiduguri and other parts of northern Nigeria in recent months. It launched an uprising in 2009 that ended with a brutal military assault which left hundreds dead.
Tuesday’s incidents come days before general elections, which will be spread over three weekends starting April 2, heightening fears of political violence in the volatile city.
On Sunday suspected sect gunmen killed the ANPP’s youth leader in the city shortly after he attended a political meeting.
In January the ANPP governorship candidate was killed by motorcycle-riding gunmen along with six others in an attack claimed by Boko Haram.
Last October the ANPP national vice chairman for northeastern Nigeria was killed by unknown gunmen at his home in the city.