ABUJA, Nigeria — A court in the Nigerian capital of Abuja on Friday convicted more than 300 terrorism suspects in a mass trial that spanned four days.

The mass trial began Tuesday, with many suspects pleading guilty to charges brought against them by the Nigerian government.

Many of them have since been sentenced to up to 20 years in prison after they appeared before a panel of 10 judges.

“In total, we brought about 508 cases. Of these 508, we were able to secure 386 convictions,” Nigeria’s attorney general told journalists after the mass trial on Friday. “We have been able to bring justice to them, or bring them to justice. So this is the clear signal that we are sending.”

Nigeria is battling a complex security crisis, especially in the north, where there is a decade-long insurgency and several armed groups that kidnap for ransom. The insurgency in the country’s northeast has lasted more than a decade.

Among the most prominent Islamic militant groups are Boko Haram and its breakaway faction, which is affiliated with the Islamic State group and known as Islamic State West Africa Province. There is also the IS-linked Lakurawa group operating in communities in the northwestern part of the country that borders Niger Republic.

There are also disputes over land and grazing between mostly Muslim Fulani herders and largely Christian farming communities frequently escalate into deadly clashes in the north-central and northwestern part of the country.

Criminal gangs who kidnap for ransom are also active.

The insurgency in the northeast has led to the death and displacement of many, according to the U.N.