Africa's most populous nation faces several security crises, including a 12-year-old jihadist insurgency in the northeast, herder-farmer clashes in the centre, kidnapping for ransom in the northwest and separatist agitation in the south.

"The first batch of A-29 Super Tucano aircraft have arrived in Kano today," Nigeria Air Force spokesman Edward Gabkwet said in a statement late Thursday.

He told AFP on Friday that six out of 12 had arrived, and the next batch would arrive in October.

The planes are built in the US by Sierra Nevada Corp. and its Brazilian partner, Embraer Defense and Security.

The $593-million (504-million-euro) deal was initially unveiled in May 2016 under former US president Barack Obama.

However, the Obama administration froze the sale just before handing over to Donald Trump, after the Nigerian military accidentally bombed a camp for people displaced by jihadist conflict in the northeast, killing 112 civilians.

Boko Haram and rival offshoot Islamic State West Africa Province (ISWAP) have killed at least 40,000 people and forced more than two million people from their homes since 2009.

The violence has spread to parts of neighbouring Chad, Cameroon and Niger, prompting a regional military coalition to fight the jihadists.

In August 2017, the State Department under Trump informed Congress it had approved the deal, which includes supplying the Nigerian armed forces with ammunition, training and aircraft maintenance.

The Super Tucano is already used in Brazil, for border patrols, and in a dozen other air forces including in Afghanistan, Colombia and Indonesia.

On Sunday, the Nigerian air force said it had lost an Alpha Jet, a European-made trainer and light attack plane built in the 1970s and 80s, after it came under fire from criminal gangs in Zamfara state in the northwest of the country.