Nigeria has convicted nearly 400 Islamist militants following mass trials held this week in the capital ​Abuja, the country's Attorney General said late on Friday.

The ‌prosecutions, which began on Tuesday, are part of a series of trials involving Boko Haram and Islamic State West Africa Province (ISWAP) suspects that started ​in 2017 with more than 2,000 defendants.

Lateef Fagbemi, Nigeria's ​Attorney General, said more than 500 cases were presented to ⁠the Federal High Court during the latest proceedings.

"We brought 508 ​cases to the court and out of this number, we ​were able to secure 386 convictions, eight discharges, two acquittals and 112 cases adjourned to the next session or phase," Fagbemi said.

Sentences ranged from five ​years to life imprisonment, and judges stipulated that the convicts ​undergo rehabilitation and deradicalisation programmes to support reintegration into society.

Boko Haram's insurgency, ‌launched ⁠in 2009 in the northeast of the country, has killed tens of thousands and displaced more than 2 million people, humanitarian groups say.

The group gained global notoriety for the 2014 mass abduction ​of schoolgirls in ​Chibok town ⁠in northeast Borno state.

Boko Haram and its splinter group ISWAP seek to establish an Islamic state ​in Nigeria and have this year increased attacks against ​the ⁠military.

International observers, including representatives from the United Nations Office on Drugs and Crime, Amnesty International, and the Nigerian Bar Association, monitored the court ⁠proceedings ​to ensure fair trials, court officials said.

The ​next phase of the trials is expected to begin by the end of ​the May quarter, said Fagbemi.