Kano - Two suicide bombers attacked a northeast Nigerian market hours after a blast outside a military barracks, as the death toll from suspected Boko Haram violence during President Muhammadu Buhari's first week in office hit 82.
Police in the Adamawa state capital Yola said two assailants approached the Jimeta Main Market and faked a fight to attract victims before blowing themselves up.
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At least 31 people were killed and 38 others injured, rescue officials said.
The Yola blast followed a suspected suicide bombing in Maiduguri, capital of neighbouring Borno state, that killed at least four people when a truck carrying firewood rammed into a checkpoint outside a military barracks.
The violence on Thursday came as Buhari ended his first foreign trip since taking office.
He visited Chad and Niger, which with Cameroon are Nigeria's key allies in the battle against an Islamist uprising blamed for 15,000 deaths since 2009.
Buhari urged closer regional security cooperation and thanked Nigeria's neighbours for their efforts to date while demanding more action from a multi-national force battling the insurgents on the frontline.
Analysts said Buhari made the trip because he cannot afford early setbacks against Boko Haram and needs Niger and Chad to ensure progress.
But the spate of bombings through his first week in office highlighted the severity of the challenge.
A new video released by the group its first for several months and first under the banner of the "Islamic State in West Africa" insisted the rebels were still to be reckoned with.
Yola had been seen as a relative safe haven in Nigeria's embattled northeast, with no confirmed Islamist attacks in several years.
With explosives strapped to their bodies, the bombers entered the Jimeta Main Market after sundown on Thursday and "pretended to be fighting", said area police spokesman Othman Abubakar.
The staged fight between the two men "attracted the attention of people nearby to see what was happening," he told AFP. "When people had gathered, they detonated their explosives."
The coordinator for the National Emergency Management Agency in Yola, Sa'ad Bello, gave casualty figures of 31 dead and 38 injured.
No group claimed responsibility but the blast bore the hallmarks of Boko Haram, who have frequently targeted crowded markets.
The Maiduguri explosion outside the Maimalari Barracks at about 5:00 pm killed four people and also resembled past strikes by the insurgents, who have made suicide attacks against the military a key feature of their uprising.
Separately, a military statement said troops had repelled attack by "a band of terrorists" and killed several late Thursday in the Borno village of Shetimari, roughly 50 kilometres (31 miles) south of the city, providing no further specifics.
Buhari was in Chad's capital N'Djamena on Thursday for talks with his counterpart Idriss Deby after visiting Niger on Wednesday.
"Your troops have stood shoulder to shoulder and fought gallantly with ours in the fight against the forces of evil," the 72-year-old former military ruler told Deby.
For his part, Deby "reaffirmed Chad's involvement and availability" to work with Nigeria.
Anglophone Nigeria has typically viewed its Francophone neighbours with suspicion, which has been blamed for the lack of a joined-up approach in tackling the militants.
The head of the Africa Programme at the London-based think-tank Chatham House, Alex Vines, said the trip underscored that Buhari "needs to make quick progress on Boko Haram and needs the support of Chad and Niger".
If Nigeria's president meets early setbacks against the insurgents, it could undermine his ability to push through "tricky reforms", including expected anti-corruption measures, he added.
"Progress in (the) northeast will help strengthen support for his mandate, which will be important," he said.
On Wednesday, the military in Abuja announced that a Nigerian officer had taken charge of the new African Union-backed Multi-National Joint Task Force based in N'Djamena.
The 8,700-strong unit, made up of military personnel, police and civilians from Nigeria, Niger, Chad and Cameroon, had been due to be deployed last November.
Buhari has ordered the military's command centre be moved from Abuja to Maiduguri, where Boko Haram was founded in 2002.
The army has since been tested with two rocket attacks on the city, as well as an explosion opposite a military facility on Wednesday, which left at least 18 dead.
There were also two suicide bomb attacks one at a mosque on Saturday that killed 26 and another on Tuesday at a cattle market, in which 13 people died.