Abuja -The head of the UN arrived in Nigeria Sunday in the wake of a suspected Boko Haram ambush on the country's army chief, to mark the Islamists' deadly 2011 attack on the global body.
Combating violent extremism is expected to be high on the agenda as Ban Ki-moon holds talks with President Muhammadu Buhari, whose inauguration in May sparked a massive upsurge in jihadist violence.
Ban's plane touched down in Abuja around 4:00 pm, an AFP correspondent saw, just hours after the army revealed Boko Haram fighters had ambushed a convoy carrying its chief-of-staff.
Lieutenant General Tukur Buratai, who was unharmed, was visiting troops Saturday when insurgents attacked in Faljari village, 45 kilometres east of Maiduguri, army spokesman Sani Usman said in a statement.
"The terrorists encountered an overwhelming firepower from the troops in which 10 of them were killed. The troops captured five terrorists," he said.
"During the encounter, sadly, we lost a soldier, while an officer and four soldiers sustained gunshot wounds."
Boko Haram has stepped up its attacks in Borno and two neighbouring states since Buhari came to power in May.
The Islamists have also carried out deadly ambushes across the country's borders and in recent weeks suicide bombers, many of them women, have staged several attacks in Nigeria, Cameroon and Chad.
The fresh wave of violence has claimed more than 1,000 lives over the last three months, dealing a setback to a four-country offensive launched in February that had chalked up a number of victories against the jihadists. - Car bombing -
An 8,700-strong Multi-National Joint Task Force, drawing in Nigeria, Niger, Chad, Cameroon and Benin, is expected to go into action soon.
Also read: Ban Ki-moon to mark jihadists attack on UN in Nigeria
Military officials have said it will be more effective than the current alliance in the battle to end Boko Haram's six-year insurgency, which has claimed at least 15,000 lives.
Ban did not make any public statements during a welcoming ceremony at Namdi Azikiwe International Airport, but he is due to hold talks with the country's state governors later on Sunday.
On Monday the UN chief will lay a wreath to commemorate the fourth anniversary of a car bombing at United Nations House, the headquarters for around 400 UN employees, that left 21 dead in the capital on August 26, 2011.
The visit will be Ban's second since taking office in 2007. He last visited Nigeria in May 2011 to discuss the crises in southern Sudan and Libya with then leader Goodluck Jonathan.
He is also due to dine with captains of industry during the two-day trip and discuss "democracy, human rights and countering violent extremism" in a meeting at the foreign ministry.
Buhari, who came to power on May 29 vowing to destroy Boko Haram, replaced his military leaders earlier in August, ordering his new chiefs-of-staff to end the insurgency within three months.
The military under Jonathan was heavily criticised for poor handling of the insurgency and its failure to free more than 200 schoolgirls abducted from the northeastern town of Chibok in April last year.
The "Bring Back Our Girls" campaign, which next week marks 500 days since the abduction, says it will hold talks with Ban during his visit, although this has not been confirmed by the government or UN.
The secretary-general will stop over in France on his return trip to discuss preparations for a major climate change conference to be held in Paris in December.