Nigeria's Defence Minister, Mohammed Badaru Abubakar, has resigned, the presidency said on Monday, with immediate effect.

Presidential spokesperson Mayo Onanuga said in a statement that Abubakar was quitting on health grounds.

"His resignation comes amid President [Bola] Tinubu's declaration of a national security emergency, with plans to elaborate on its scope in due course," the spokesperson said.

Nigeria's armed banditry is a security crisis

Nigeria has long been plagued by mass kidnappings, but the past weeks have seen a surge in attacks and abductions by armed bandits.

Most recently, gunmen attacked a church in Kogi state in central Nigeria, abducting the pastor along with nearly a dozen worshipers during a Sunday morning service.

On Saturday, some 30 women, including a bride and visiting wedding guests, were kidnapped in Sakoko in northwestern Nigeria.

In all, some 490 people have been abducted across multiple states in the past two weeks, according to Nigeria's Punch newspaper.

A large number of these were from the St. Mary's private Catholic boarding school in Papiri, Niger State, where 315 people, mostly children, were abducted in late November. Around 50 children managed to escape.

Armed bandits, often operating in Nigeria's northwest and north-central regions, frequently carry out kidnappings for ransom. 

As well as banditry, Nigeria is also battling a deadly Islamist insurgency in its northwestern regions.

But the Nigerian government has long been criticised for failing to stem the security crisis and protect schools in particular.

Security forces stretched thin

In the wake of the kidnappings, President Tinubu declared a security emergency and ordered mass recruitment of police and military personnel.

But the military and police are already low paid, lacking in equipment and in need of training.

"In remote villages and towns, state security agents are virtually non-existent and surveillance remains very poor," finds Oluwole Ojewale, Regional Coordinator for the Institute for Security Studies, an African think tank, in an analysis.

Nigeria has only approximately 370,000 officers to protect its 220 million citizens, according to a UK government assessment, and significant numbers of these are seconded to protect wealthy individuals.

Corruption and bribery are commonplace, while police response to crimes is often slow, the assessment finds.