More 50 fifty people were killed in the north-eastern Nigerian town of Bama on May 7. The army suspects the attacks were carried out by Islamist militants Boko Haram.
Around 200 heavily-armed assailants stormed an army barracks, a police station and a jail, freeing more than 100 prisoners.
In a separate incident on May 9, more than 40 police officers were killed in an ambush in the central state of Nassarawa. The governor believes a local gang could be behind the attack.
Human rights groups suggest that tribal loyalties are at the root of Nigeria’s lack of stability.
Lawyer and human rights activist Ememanka Onyebuchi said: “People are more inclined to identify with their tribal blocks than with the country as a whole, and that is one of the tragedies of this nation.”
Nigeria’s President Goodluck Jonathan cut short a trip abroad on May 9 – to return home in the wake of this week’s violence.