Kidnapping for ransom is common in the oil-rich Niger Delta region, where militant groups have waged a war against the federal government.
Tramadol, which is available on prescription in the UK, is the most abused drug in Egypt, with as much as 40% of the population using it.
This is the worst attack in Africa's history since Al-Qaeda was blamed for twin attacks on US Embassies in Kenya and Tanzania in 1998, when 220 people died.
Italian priest Maurizio Pallu has been kidnapped by gunmen during a robbery in Nigeria's southern Benin City.
New research says factors such as rape and slavery fuel terrorism globally and provide fertile ground for captives to develop feelings of sympathy for and loyalty to abductors.
The insurgency has affected the north-east Borno state most acutely, with 2,300 teachers killed and nearly 1,400 schools destroyed since 2009.
Most were under 15 years old, the UN agency said.
"Terrorists and criminals must be fought and destroyed relentlessly," said Buhari.
In a video, Shekau also called on Muslims to rise up for jihad.
University in Maiduguri, epicentre of Boko Haram's insurgency, targeted at least eight times since January.
There are conflicting reports on the number of attackers who opened fire.
Rescue operations to free abducted oil contractors ends in dozens of deaths in restive Borno state.
NNPC is conducting research operations in the area following crude oil discovery in restive north east.
Boko Haram renowned for kidnapping women and children and forcing them to carry out suicide bombing missions.
The refugees were returning to their village, which has been declared a 'no-go zone' following Boko Haram violence.
A day after the Niger attack, some 700 Boko Haram militants in Nigeria's Borno state surrendered to the police.
Shekau made remarks as insurgency continues to claim lives in Nigeria and neighbouring countries.
Boko Haram releases video through journalist Ahmad Salkida claiming responsibility for abduction and ambush.
Leader of Isis-affiliated group offered to free kidnapped priest in exchange for his parents, held by police.
Militants and security forces engaged in a 30-minute long fight in restive Borno state.
The CJTF helped to turn the tide against Boko Haram, but their presence now casts a shadow over longer-term efforts to bring stability to the troubled Lake Chad region.
Leader of Abu Sayyaf is one of the most wanted terrorists in both the Philippines and the US.