Kano - Forty-eight soldiers were killed in a Boko Haram attack in remote northeast Nigeria, military sources said on Monday, in the latest strike that raises questions about the group's apparent resurgence and troops' ability to fight back.
Scores of jihadist fighters in trucks stormed the base on Thursday in Zari village in northern Borno state and briefly seized it after a fierce battle.
Boko Haram, which has been waging a deadly insurgency in northeast Nigeria since 2009, has intensified attacks on "hard" military targets in recent months, undermining repeated claims by the military that they have the upper hand.
Troops have even protested that they are stretched to breaking point by constant security duties and the attacks that analysts tracking the conflict say have become more sophisticated and planned.
At least 30 Nigerian soldiers were initially said to have been killed in Thursday's raid, which was claimed by a Boko Haram faction backed by the Islamic State group.
"The casualty toll now stands at 48 with the recovery of 17 more bodies of soldiers in surrounding bushes in Zari by search and rescue teams," a military source who did not want to be named told AFP.
"Search operations are still ongoing and more bodies are likely to be recovered."
Another military source confirmed the new death toll.
"So far (the) bodies of 48 troops have been recovered. Yesterday rescue teams found 17 bodies of fallen soldiers," he said, adding that they included two officers and 46 soldiers.
"When the troops were overwhelmed by the terrorists they withdrew in different directions."
- Upsurge in activity -
The militants were said to have taken weapons and military equipment before they were pushed out of the base by troops with aerial support. The sources said the extremists were pursued and bombarded by a fighter jet.
"The terrorists also suffered heavy casualty from the bombardment," one of the military officers said.
Zari is located 30 kilometres (20 miles) from the town of Damasak, on the border with Niger, which has seen an upsurge in Boko Haram activity.
The jihadists are thought to have attacked the base from the nearby Garunda village, where 17 troops were killed and 14 injured in an attack on another military base last month, the sources said.
In a statement late Friday the Nigerian military confirmed troops fought Boko Haram "insurgents... on (a) rampage to loot the community and extort money from villagers". But no death toll was given.
The intensified armed campaign in recent weeks, primarily against military targets, has claimed the lives of dozens of troops, providing the government with a headache as it looks to trumpet its security achievements before elections next year.
On July 14, militants overran a military base in Jilli village in neighbouring Yobe state. Dozens of troops were said to have been killed, wounded or missing.
The army at the time conceded the base was attacked but again said troops remobilised and succeeded in repelling the attackers.
In a short statement last Wednesday, IS-affiliated Boko Haram jihadists claimed to have killed "several" Nigerian troops in separate mortar strikes on a military base in the town of Arge in the Lake Chad area.
AFP could not independently verify the claim .
The Boko Haram insurgency, which is in its ninth year, has left 20,000 people dead and displaced 2.6 million.