Police have confirmed that two attackers were shot dead and four police officers were killed when Nigeria's Islamist sect Boko Haram stormed the central jail in Damaturu, the capital of the northeastern state of Yobe, on 24 June freeing 40 inmates.
It followed the 19 June gun battle between suspected Boko Haram members and security forces in Damaturu, which resulted in at least 40 casualties.
The Boko Haram sect, which is based in the remote northeast, is now regarded as the country's biggest security threat.
Since the movement began its uprising two years ago, with a goal to carve out an Islamist state, it has been held responsible for multiple gun and bomb attacks that have killed hundreds.
In recent times there has been escalating violence in the country's northern region. Three suicide bombings at churches in the northern Kaduna state on 17 June killed over 20 people and triggered revenge attacks from Christians who reacted by burning down mosques and killing dozens of Muslims.
In the face of mounting criticism of his handling of the violence, Nigeria's president Goodluck Jonathan fired his national security adviser General Owoye Azazi and defence minister Haliru Bello on 22 June. Azazi was replaced immediately by retired Nigerian colonel Sambo Dasuki, reported to have previously acted as aide-de-camp to the country's former military dictator Ibrahim Babangida. Bello’s post has not yet been filled.
Boko Haram is said to be gaining support in particular among the unemployed young at a time when poverty is increasing in a country split between Muslims in the north and Christians in the south.
The US recently branded the head of the main branch of the organisation, Abubakar Shekau, a "global terrorist".