Al-Qaeda in the Arabian Peninsula has taken advantage of the war in Yemen to launch attacks against military forces in the country.

Commander Abd al-Latif al-Sayyid and the three fighters from the Security Belt Forces, an armed group loyal to Yemen’s secessionist Southern Transitional Council, were killed in an explosion while travelling in a convoy through southern Abyan governorate, the three officials and the witness said.

The four said they believed al-Qaeda in the Arabian Peninsula (AQAP) was responsible for the attack, but provided no further details. All spoke on condition of anonymity out of fear of reprisal.

The separatist council is backed by the United Arab Emirates and controls much of Yemen’s south. Despite also fighting the Houthi rebels, it is at odds with the internationally recognised government, and has repeatedly called for the country to be split into two, as it was until 1990, when North and South Yemen united to form the Republic of Yemen.

AQAP has not claimed responsibility for Thursday’s attack but is active in Abyan province and regularly carries out ambushes against Yemeni forces. AQAP is seen as one of the more dangerous branches of the wider al-Qaeda network.

Earlier this month, security officials told The Associated Press that AQAP fighters killed five troops from the Southern Armed Forces, a large force loyal to the Southern Transitional Council.

Last month, suspected AQAP fighters clashed with secessionist forces in the governorate of Shabwa. Three were killed in the clash, including two secessionist fighters.

Yemen’s ruinous civil war began in 2014 when the Iran-backed Houthi rebels seized the capital of Sanaa and much of northern Yemen and forced the government into exile. A Saudi-led coalition, including the UAE, intervened the next year to try to restore the internationally recognised government to power.

AQAP has since exploited the country’s years-long conflict to cement its presence in the impoverished nation.