Nigerian President Muhammadu Buhari took to state TV on Monday in his first speech since returning from a long medical absence in Britain, in a bid to dampen mounting separatist tensions in the country.
The 74-year-old, who received treatment for an undisclosed condition in London, appeared thinner than usual as he read slowly from a prepared statement in which he also vowed to redouble the fight against Boko Haram jihadists.
He did not address his more than three-month absence or the illness that caused him to seek treatment abroad.
"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," said 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 appearing in images meeting a private army of young men.
Arewa, a radical Muslim youth group in the country's north, has issued an October 1 deadline for all Igbo people to leave the region.
Boko Haram jihadists, meanwhile, have been fighting a bloody insurgency in the country's northeast since 2009.
Buhari vowed renewed energy for the fight against "terrorists and criminals", singling out Boko Haram, kidnappers and those responsible for ethnic violence.
Don Ekereke, a security analyst, accused Buhari of lacking a concrete plan.
"After more than 100 days we were expecting more details on how he's intending to lead the country. Im not alone to say that it isn't inspiring," he told AFP.
"There is no doubt that the security situation has deteriorated since the beginning of the year: Boko Haram is worsening, kidnappings are increasing," he added.
"We really hope that all the security agencies... will not be overzealous (after the speech) just to impress their master."
But Bismarck Rewane of the Lagos-based Financial Derivatives Company said Buhari's return was good news for the security situation and the economy.
"His return will strengthen security, and if that is resolved investors will start coming back. There's been no investment lately because of political insecurity," he said.
The president left for London on May 7, and his prolonged absence fuelled tensions back home, where calls grew for him to either return or resign.
Buhari, who said he was "pleased to be back on home soil", also called for renewed efforts to transform the country's sclerotic economy, which is in the grip of its worst recession for more than two decades.
Buhari, a retired general who headed a military regime in the 1980s, has been dogged by speculation about his health since June last year, when he first went to London for treatment.
He then spent nearly two months in London in January and February, saying upon his return in early March that he had "never been so ill".
Since August 7, there had been a series of protests in Abuja demanding that Buhari return or quit if he was unable to go on.
The rallies turned violent last Tuesday when mainly ethnic Hausa traders pelted protesters with stones, prompting them to abandon their daily vigils.
Robert Besseling, an analyst at the consulting firm EXX Africa, said that Buhari's return had fired the starting pistol on the 2019 election campaign.
"In the immediate future, President Buhari's return will put to rest rumours that he will not run for re-election in 2019," he said in a note issued ahead of Monday's speech.