Curfews were ordered across several northern states on Friday after clashes erupted the previous day.

Security forces have fired tear gas to break up protests in the Nigerian capital, Abuja, as nationwide demonstrations against economic hardship continue.

Curfews were ordered across several northern states on Friday after clashes erupted in the cities of Kano and Abuja the previous day.

Protesters say they are demonstrating over food shortages and accusations of misgovernment and corruption in Africa’s most populous country.

Photos of the protests show Nigerians holding placards with slogans such as “end bad governance in Nigeria”, “payment of living wage to all Nigerian workers in public and private employment”.

Police said that more than 300 protesters were arrested and curfews imposed in five northern states after the looting of government and public properties.

Rights group Amnesty International said at least 13 protesters had been killed in three northern states. The authorities have not commented on any deaths.

Nigeria’s inspector general of police said late on Thursday that the military could be called in for help.

The country had placed all police units on “red alert” and further measures could be taken to restore order, Inspector General Kayode Egbetokun said in a statement.

“The police are equipped to respond appropriately to the unfolding situation and will get assistance from other security agencies, including the military if the need arises,” the statement reads.

Amnesty International said security forces were responsible for the deaths of the 13 people in Niger State, Maiduguri, which is the capital of Borno State, and Kaduna, all in the north.

“Our findings, so far, show that security personnel at the locations where lives were lost deliberately used tactics designed to kill while dealing with gatherings of people protesting hunger and deep poverty,” it said.

Kaduna State police spokesperson Mansur Hassan said on Thursday that the police had fired tear gas at protesters but had not used live ammunition.

Reporting from Lagos, Nigeria’s economic hub, Al Jazeera’s Ahmed Idris said the number of protesters on the streets on Friday appeared smaller than the previous day.

“The participation or the numbers we’re seeing here are far less than what we saw yesterday,” he said.