At least seven troops have been killed as militants linked to Boko Haram and ISWAP launched an assault in Borno State

Islamist fighters have attacked a Nigerian Army base near the border with Chad, leaving seven troops dead, including a commanding officer, Reuters has reported, citing military sources.

The raid on Sunday targeted the 242 Battalion facility in Monguno, Borno State, where at least 12 militants were reportedly killed in the ensuing clash. The attackers, who arrived on motorbikes, were said to belong to Boko Haram and its breakaway faction, Islamic State West Africa Province (ISWAP).

The West African state has long struggled with criminal gangs and extremist groups, which frequently hold people for ransom. The most prominent incident came in 2014, when Boko Haram militants kidnapped hundreds of schoolgirls from Chibok in Borno State.

According to Reuters, citing anonymous military sources, the base commander, who was close to retirement, was among those killed on Sunday. Six soldiers reportedly died when their vehicle struck an improvised explosive device as they attempted to reinforce the position during the assault.

The assault came shortly after a series of coordinated attacks on other army positions across the region. Nigerian authorities said on Thursday that an army general and several troops were killed in another overnight attack by Boko Haram and ISWAP fighters on the headquarters of the 29 Task Force Brigade in Benisheikh in Borno State. Local media reports indicated that Brigadier General Oseni Omoh Braimah, commander of the brigade, was among those killed.

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Nigeria declared a national security emergency in November amid the deteriorating situation. The US, which has stepped in to support Abuja's campaign against Islamic State-linked militants, has warned its citizens against traveling to the West African country, citing terrorism and armed violence.

Earlier, a string of suspected suicide bombings rocked Maiduguri, the capital of Borno State, killing at least 23 people and injuring 108 others. Police said the blasts hit a market, the gate of the University of Maiduguri Teaching Hospital, and the city's post office area in March.