AT LEAST 13 protesters have been killed in Nigeria as mass demonstrations against the country’s economic crisis turned violent in several states, Amnesty International said today.

Four of the protesters were killed by a bomb explosion in the north-eastern state of Borno that also left 34 injured, police said on Thursday night.

More than 300 demonstrators were arrested and curfews imposed in the northern states of Kano and Katsina after government and public properties were looted, the police added.

One officer was killed and several injured.

Amnesty International’s Nigeria director Isa Sanusi said in an interview that the group independently verified deaths that were reported by witnesses, families of the victims, and lawyers.

The protests were mainly over food shortages and allegedly bad governance.

Frequently accused of corruption, Nigeria’s public officials are among the best paid in Africa, though the country has some of the world's poorest and hungriest people despite being one of the continent’s top oil producers.

Protesters said they wanted the reinstatement of gas and electricity subsidies, whose removal, as part of unpopular government reforms intended to boost the economy, has had a knock-on effect on the price of just about everything else.

An earlier bombing in Borno killed at least 16 people on Wednesday at a roadside market in Kawori, a rural community in the Konduga area of the state. Dozens more were wounded.

The government imposed a 24-hour curfew after the bomb attack, the second in recent weeks.

No-one immediately claimed responsibility for the blast, but analysts and some local officials suspected Islamist militant group Boko Haram, which has waged an insurgency in Nigeria since 2009.