The Nigerian army has announced it has recaptured a key town on the border with Cameroon from Boko Haram terrorists. Gamboru Ngala, in the restive Borno state, had been under control of the the terrorists since mid 2014.

In May that year, the insurgents attacked the town killing at least 300 people in a 12-hour onslaught. The insurgents were briefly pushed out of the city by Cameroonian troops in February 2015, but regained control shortly after.

"The Nigerian army has retaken the economic and strategic town of Gamboru Ngala, Borno State, from the Boko Haram terrorists group today," military spokesman Colonel Sani Kukasheka Usman said in a statement, according to AFP. "The triumphant troops are now busy with clearing and mopping up patrols."

Who are Nigeria's Boko Haram terrorists?

Boko Haram (recently renamed Iswap) fights against Western influence in Nigeria and aims to impose its version of Sharia law on the country. The group declared an Islamic caliphate in Gwoza, along the Cameroon border, in August 2014.

Boko Haram has raided several cities in the north of the country in a bid to take control of more land.

Three states − Adamawa, Borno and Yobe − have been under a state of emergency since May 2013, due to Boko Haram's attacks.

The group has killed more than 2,600 people since the beginning of 2015.

Boko Haram has killed thousands of people in northern Nigeria and neighbouring countries since its insurgency became violent in 2009. In August, the Nigerian army announced a new task force – consisting of 8,700 troops from Nigeria, Niger, Chad, Cameroon and Benin – was ready to step up the fight against the terrorists.

Meanwhile, unconfirmed reports that the group's leader Abubakar Shekau had been replaced started circulating after Shekau failed to appear in the group's latest propaganda videos, triggering speculation regarding his fate.

Nigerian intelligence also warned that some Boko Haram members have been found in the commercial capital of Lagos, suggesting that the terrorists are spreading beyond the country's north.

Speaking to IBTimes UK, defence spokesman Rabe Abubakar said: "We have a wide network of intelligence in the country and whatever the security agency said regarding the issue of Boko Haram should not be underestimated."

He added, however, that the military is aware of Boko Haram movements and that the terrorists had been weakened by the ongoing regional offensive. "Those elements are not a threat to us and our citizens."We know what they are doing and where they are going," he said.