Nigeria's army may have ramped up its fight against Boko Haram, but it appears the militants are still making advances. Boko Haram fighters reportedly seized control of a strategic border town Friday in northern Nigeria, the same day that the Islamic State released images praising the group's actions in West Africa.

Approximately 2,000 fighters invaded the town of Marte on Thursday, according to local resident Imamu Habeeb, who told AFP that the militants battled with the Nigerian military overnight and managed to drive out the soldiers that were stationed there by Friday. Habeeb claimed that the militants were heavily armed with bombs and tanks and killed several people, although he did not specify whether the victims were civilians or soldiers.

Marte is located in the northeastern Borno state on the border with Lake Chad. The area has been the site of some of the fiercest fighting between Boko Haram and the Nigerian military, aided by coalition forces from nearby Niger, Chad, and Cameroon.

Marte has been under Boko Haram control previously three other times, but the group was driven out in recent weeks by the Nigerian military. On Thursday, the military launched a ground operation into the Sambisa forest, a key Boko Haram stronghold, but were forced to retreat after discovering it was littered with land mines.

Boko Haram has been waging a bloody insurgency for the past six years, killing thousands of people and destabilizing Nigeria and much of the surrounding region. Boko Haram started out firmly rooted in Nigeria and originally sought only to gain control over several provinces in the north. But in the past year, the group has been expanding its attacks to outside the country and strengthening its ties with global Islamist groups, including the Islamic State.

On Friday, the Islamic State reportedly released images on social media praising Boko Haram fighters as martyrs. According to the BBC, the Islamic State referred to Boko Haram as ISWAP, short for the Islamic State's West Africa Province. Boko Haram leader Abubakar Shekau pledged allegiance to the Islamic State in March.

Boko Haram has also borrowed tactics from IS, including their use of social media and propaganda videos to document their activities and spread their message. Over the past several months, Boko Haram has released several high-quality videos that appear similar to the ones frequently posted by the Islamic State.

It's unclear whether the Islamic State is helping Boko Haram militarily or if their alliance is merely an ideological one, but IS-affiliated groups have gained significant strength in Libya in recent months, and the relationship with Boko Haram suggests the possibility of a significant IS expansion far beyond strongholds in Syria and Iraq and into West Africa.