Brig Gen Carsten Jacobson, spokesman for the NATO-led International Security Assistance Force, said an investigation had been launched.
Brig Gen Wissam al-Hassan was viewed as one of the leading Sunni figures in Lebanon.
At a news conference, Brig Gen Jim Lukeman said the cause of the malfunction was under investigation.
Isaf spokesman Brig Gen Carsten Jacobson said that Nato could not yet reveal the identity of those killed.
Last week, senior army officer Brig Gen Manaf Tlas fled Syria via Turkey.
Military spokesman Brig Gen Domingo Tutaan said the early morning gun battle raged for an hour in a village on the outskirts of Patikul.
Fire brigade chief Brig Gen Ali Ahmed Khan said crews had seen bodies lying on the ground inside, but that "no-one was seen alive".
But Brig Gen Edokpaye disputed this, saying Boko Haram's weapons had exploded, causing "fire to about 30 thatched houses in the predominantly fishing community".
Brig Gen Joseph Nzabamwita told the BBC they were undergoing re-education.
Baga is close to the border with both Chad and Niger and a multinational force from the three countries was attacked, its commander Brig Gen Austin Edokpaye said.
In Kirkuk, 250km (150 miles) north of Baghdad, four bombs were planted near the house of a military officer, the city's police commander, Brig Gen Sarhad Qadir, told AP.
Nigerian military spokesman Brig Gen Olukolade said the army would continue its operation "as long as it takes to achieve our objective of getting rid of insurgents from every part of Nigeria".
BBC: Nigeria army's offensive to continue 'as long as it takes'
After the earlier roadside bomb in Kandahar, Isaf spokesman Brig Gen Gunter Katz said it had been a "difficult week" for the coalition, but added that the deaths would not change its commitment to the task in Afghanistan.
Firefighting chief Brig-Gen Naseh Mohammed put the death toll as high as 30.
Last week, it emerged that Brig-Gen Tlas had escaped Syria via Turkey, in what correspondents described as a significant blow to the Assad regime.
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