Nigerian troops were forced to retreat from Sambisa Forest as they took the battle to the stronghold of Islamist sect Boko Haram, after a landmine blast killed one soldier and three vigilantes.
The Military said on Wednesday that soldiers were conducting offensives “in some forest locations” in the area after it was announced last week that the operations were imminent.
Defence spokesman Chris Olukolade said in a statement that a senior Boko Haram commander was killed, as well as a number of militants who attacked a patrol.
“The operations especially in forest locations are progressing in defiance of obstacles and landmines emplaced by the terrorists,” he added.
However, progress has been hampered by improvised explosive devices with which the area has been rigged by the terrorists, a civilian vigilante involved in the operation told AFP in an account backed by a security source.
“Boko Haram have buried landmines all over the routes leading to their camps in the forest, which is no doubt a huge obstacle retarding the military offensive against them,” he told AFP.
“We decided to turn back since the route was unsafe. As we were driving back, one of the vehicles carrying CJTF (Civilian Joint Task Force) hit a mine,” he added.
“A soldier and three CJTF were killed while another soldier was injured. We trudged along and made it back to Bama on Wednesday.”
The vigilante added: “There are no soldiers in Sambisa right now. We all returned to Bama after the horrifying experience of manoeuvring through minefields.”
“Boko Haram are in large numbers in Sambisa,” said the vigilante, who requested anonymity for security reasons.
“All their fighters who were pushed out of Bama, Dikwa, Gwoza and Damboa (in Borno state) all moved to Boko Haram camps in Sambisa,” he added.
The Sambisa Forest is located in Borno state, some 80 kilometres (50 miles) from the town of Chibok, where more than 200 schoolgirls were kidnapped on April 14 last year.
It has been claimed that the 219 schoolgirls still being held were initially kept in the former game reserve, although others have said they may have been split up and moved to Chad or Cameroon.