Multiple explosions and gunfire on rocked two northeastern Nigerian cities on Thursday, both of which have previously been badly hit by violence blamed on Islamist group Boko Haram. It was unclear whether there were casualties in the cities of Maiduguri and Damaturu. Six blasts and gunfire hit Maiduguri, residents and a military source said, after explosions and shooting earlier broke out in Damaturu. \"There has so far been six explosions, and four of them in the same area,\" the military source said, adding a shootout had also occurred. Residents reported that people were fleeing in Maiduguri, but it was unclear whether there were casualties. One witness said one of the explosions shattered the windows of a mosque in an office complex. In Damaturu, a police officer said gunmen opened fire on a checkpoint, but the attack was repelled. Residents said explosions and gunfire broke out in the afternoon and was still occurring a couple hours later. Police could not immediately be reached for comment. \"For the past 40 minutes, there have been explosions and shootings around the Pompomari area of the city,\" Damaturu resident Kabiru Musa said by telephone in the afternoon. \"Most people have moved indoors and it is not really clear whether it is an attack or a shootout with police and Boko Haram.\" Another resident said it appeared suspected Boko Haram members were in the streets shooting and setting off explosions at random. Maiduguri has borne the brunt of the violence attributed to Boko Haram, which has claimed responsibility for scores of attacks in the north as well as the August suicide bombing of UN headquarters in the capital Abuja that killed at least 24. A military task force has deployed in Maiduguri in a bid to stop the sect, but it has in turn been accused of major abuses, including shooting civilians and burning their homes in the wake of bomb attacks. Damaturu was hit by coordinated attacks in early November claimed by Boko Haram which left some 150 people dead. Earlier this week, blasts at a house in Damaturu rented by suspected members of Boko Haram left one dead and several wounded. Boko Haram launched an uprising in 2009 put down by a brutal military assault which left some 800 dead as well as its mosque and headquarters in Maiduguri in ruins. It went dormant for about a year before re-emerging in 2010 with a series of assassinations. Bomb blasts have since become frequent and have grown in sophistication. There has been intense speculation over whether Boko Haram has formed links with outside extremist groups, including Al-Qaeda\'s north African branch. The group is believed to have a number of factions with varying aims. Nigeria is Africa\'s most populous nation with some 160 million people, roughly divided between a mainly Muslim north and predominately Christian south.