Gunfire has erupted and jailbreaks have been reported in Nigeria, as unrest over the shooting of protesters in its biggest city continues. Rights group Amnesty International said security forces killed at least 12 people in Lagos on Tuesday. Nigeria's army has denied killing demonstrators in the Lekki area, provoking more anger. The shooting has spurred global calls for those responsible to be held to account. Earlier, Nigeria's vice-president promised justice for victims shot during protests against police brutality. Lagos and other parts of Nigeria have seen buildings torched, shopping centres looted and prisons attacked since the shooting. The state government in Lagos imposed an indefinite round-the-clock curfew on the coastal city's 20 million inhabitants on Tuesday evening. Other states have taken similar action, including Anambra, which ordered a 24-hour curfew on Thursday. The protests began about two weeks ago with mostly young people demanding the disbandment of a notorious police unit, the Special Anti-Robbery Squad (Sars). Using the hashtag #EndSars, protesters rallied crowds to the streets. Earlier this year, Amnesty said it had documented at least 82 cases of torture, ill treatment and extra-judicial execution between January 2017 and May this year against members of Sars. Nigerian President Muhammadu Buhari disbanded Sars on 11 October. But protests have continued, morphing into demands for wider reforms to the police and the government.