A Nigerian court sentenced four members of Islamist sect Boko Haram to life imprisonment on Tuesday for their role in three deadly attacks carried out with industrial explosives near the capital Abuja in 2011.
Another Boko Haram militant was given 10 years while a sixth was freed for lack of evidence. All were tried under criminal laws predating a 2011 Terrorism Prevention Act that prescribes the death penalty.
Boko Haram has been fighting since 2009 for an Islamic state in religiously mixed Nigeria. The insurgency has left more than 3,000 dead, rights groups say, and is seen as the number one security threat to Africa's leading energy producer.
Judge Billisu Aliyu sentenced Shuaibu Abubakar, Salisu Ahmed, Umar Babagana-Umar and Mohamed Ali to life for their role in a bombing of the electoral commission offices in Suleja, a satellite town of Abuja, on April 8, 2011. That blast, a week before presidential elections, killed 16 people.
They were also sentenced for a bombing at a political rally on March 3 that year that killed three people and another at a church gathering that killed three four months later, both of them in Suleja. Co-conspirator Umar Ibrahim got 10 years.
"They used explosives meant for blasting rocks for mining purposes to kill human beings who had done nothing against them," Aliyu said, summing up before pronouncing the sentence.
"The convicts have shown lack of respect for human life. They deserve to be removed from the society."
Nigerian President Goodluck Jonathan declared Boko Haram a terrorist group last month, meaning that anyone who supports them can get a 20-year jail term and anyone who plots a deadly attack with them faces the death penalty.
Since May Nigerian forces have been on a concerted offensive to flush Boko Haram out of its northeast Nigeria strongholds. Security sources say attacks by the sect are down, but they have continued sporadically.
Suspected Islamist gunmen killed 27 students and a teacher in a boarding school in the northeast town of Potiskum on Saturday.
Another Boko Haram member, Kabiru Sokoto, is on trial over a Christmas Day bombing in 2011 that killed 37 people at Catholic church in Madalla, also on the outskirts of Abuja.