Nigerian President Muhammadu Buhari has appealed to those taking part in widespread demonstrations to "resist the temptation of being used by some subversive elements to cause chaos".
"For you to do otherwise will amount to undermining national security and the law and order situation. Under no circumstances will this be tolerated," he said in a televised speech.
The broadcast was Mr Buhari's first public address to the nation since security forces were accused of gunning down peaceful protesters in Lagos on Tuesday.
But he failed to make any direct mention of the incident that has helped unleash chaos in Africa's biggest city and fuelled popular ire.
The president shrugged off condemnation from the US, African Union, European Union and Britain over the excessive use of force by the authorities.
"We thank you and urge you all to seek to know all the facts available before taking a position or rushing to judgement and making hasty pronouncements," the president told the international community.
The spreading of "deliberate falsehood and misinformation, in particular through social media" was, he said, "a ploy to mislead the unwary within and outside Nigeria into unfair judgement and disruptive behaviour".
Pictures and videos of shots being fired on a crowd of around 1,000 protesters in Lagos by security forces on Tuesday were widely shared on social media, unleashing a wave of anger towards the authorities.
Protests against police abuse and bad governance were largely peaceful when they began on October 8, but violence erupted and escalated in recent days.
Amnesty International said 56 people had died in the unrest across the country.
The president said he was deeply pained that innocent lives had been lost but did not respond to claims that the Nigerian army and police were behind some of the killings.
A protester holds a stained Nigerian flag along a road during a protest against the Nigeria rogue police, otherwise know as Special Anti-Robbery Squad (SARS). Source: AP
Instead, he warned those he said had "hijacked and misdirected the initial, genuine and well-intended protest of some of our youths in parts of the country".
Nigeria, where many live in extreme poverty and where the median age is 18, is a tinderbox of economic and social grievances.
The 77-yeard-old Mr Buhari called on the youth to "discontinue the street protests and constructively engage government in finding solutions."
"Your voice has been heard loud and clear and we are responding," he said.
At least 12 people were killed by the Nigerian army and police in two locations in Lagos on Tuesday in a deadly crackdown on demonstrations, Amnesty International said.
Peaceful protesters had gathered despite a curfew imposed to end spiralling protests over police brutality and deep-rooted social grievances.
"Evidence gathered from eyewitnesses, video footage and hospital reports confirm that between 6:45pm (4:45am AEDT) and 9:00pm (07:00am AEDT) on Tuesday 20 October, the Nigerian military opened fire on thousands of people," Amnesty said in a statement.
The Lagos governor at first insisted no fatalities had been recorded but later said the authorities were investigating the death of one person resulting from "blunt force trauma to the head".
He said at least 25 others were wounded.
The shooting drew international condemnation, with UN High Commissioner for Human Rights Michelle Bachelet saying reports suggested it could have been premeditated.
"There is little doubt that this was a case of excessive use of force, esulting in unlawful killings with live ammunition, by Nigerian armed forces," she said.
"Reports that CCTV cameras and lighting were deliberately disabled prior to the shooting are even more disturbing as, if confirmed, they suggest this deplorable attack on peaceful protestors was premeditated, planned and coordinated."
