Nigerian President Muhammadu Buhari took to state TV on Monday in his first speech since returning from a long medical absence in Britain, saying separatists calling for the breakup of Nigeria have crossed a red line and the country's unity is not negotiable.
"I was distressed to notice that some of the comments (in my absence), especially in the social media have crossed national red lines by daring to question our collective existence as a nation. This is a step too far," he said.
"The national consensus is that it is better to live together than to live apart," added Buhari, who returned to Nigeria on Saturday after more than 100 days away from the west African nation of 190 million people.
Nigeria is facing a number of breakaway movements, including the Indigenous People of Biafra led by fierce Buhari critic Nnamdi Kanu in the country's southeast which is dominated by the Igbo ethnic group.
The group has become increasingly vocal in its bid to win independence in recent weeks, with Kanu previously appearing in images meeting a private army of young men.
Arewa, a radical youth group in the country's north, has issued an October 1 deadline for all Igbo people to leave the region.
Boko Haram jihadists have meanwhile been fighting a bloody insurgency in the country's northeast since 2009 in a bid to establish a hardline state, a battle that has so far claimed at least 20,000 lives and forced some 2.6 million others to flee their homes.
Buhari, 74, who took office in May 2015, handed over power to his deputy, Christian southerner Yemi Osinbajo, when he traveled to Britain on May 7 for treatment of an unspecified ailment.
In his televised speech, Buhari vowed renewed energy for the fight against "terrorists and criminals", singling out Boko Haram, kidnappers and those responsible for ethnic violence.
"We will tackle them all," he said.