Nigeria has turned to Russia and Pakistan to purchase warplanes following the US refusal to sell aircraft to the West African nation. Air Marshal Sadique Abubakar said Nigeria bought warplanes and helicopters that will be used to counter terrorism in the country.

Nigeria has been fighting a seven-year-long insurgency by Boko Haram terrorists, blamed for the death of at least 20,000 people.

The country is also witnessing renewed violence in the oil-rich south-east, where militant groups have been disrupting oil and gas production by bombing facilities and pipelines.

The US is supporting the Nigerian army by providing training and intelligence assistance, but has refused to sell aircraft and weapons to Nigeria as it is concerned over alleged human rights abuses committed by the army.

The embargo is part of the Leahy Law, which forbids the US from providing military assistance or funding to countries that commit – or are suspected of committing – gross human-rights abuses with impunity.

Nigeria's President Muhammadu Buhari has often criticised the arms ban. Earlier this year, Nigeria said the ban should lifted as the country's human rights record had improved.

Who are Nigeria's Boko Haram?

Boko Haram, which has renamed itself Iswap, fights against Western influence in Nigeria and aims to impose its version of Sharia law throughout occupied territories.

The group launches attacks in Nigeria and neighbouring countries in a bid to take control of more territory. Three Nigerian states – Adamawa, Borno and Yobe − have been under a state of emergency since May 2013.

Boko Haram has killed more than 20,000 people since 2009 and was deemed the world's deadliest terror group, surpassing Islamic State in November 2015. Nigeria has also become the world's third-most terrorised country as a result of the group's violent insurgency.

The US said it was considering lifting its arms ban.

In October, outgoing US leader Barack Obama reiterated his country "continues to support the governments and people of the Lake Chad Basin region in their ongoing struggle to defeat Boko Haram".

Abubakar said Nigeria's air force was assisting the army and navy in countering activities of terrorists and militants, Reuters reported.

He added more than 700 of his troops were undergoing training in Pakistan, China, the UK, South Africa, Egypt, Russia and the US.

In addition to its own military operation Lafiya Dole, Nigeria is now leading a regional offensive – consisting of 8,700 troops from Nigeria, Niger, Chad, Cameroon and Benin – against Boko Haram.

The offensive has scored some successes, such as the recapture of key territories and the release of thousands of civilians held captive by the group.

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The Nigerian army has been accused of committing war crimes against detainees during the fight against Boko haram terrorists Getty