SANAA, Yemen — A government warplane bombed an army position in southern Yemen, killing at least 30 soldiers involved in months of intense battles against al-Qaida members, officials said Sunday.

The strike appeared to be a mistake, but the soldiers hit were from a unit that had defected to side with protesters seeking the president’s resignation, raising questions about whether the bombing might have been intentional.

Yemen’s government and the renegade military units both consider Yemen’s al-Qaida branch an enemy. But the president’s political opponents accuse him of allowing Islamic militants to seize control of towns in southern Yemen earlier this year to spark fears in the West that without him in power, al-Qaida would take over.

The airstrike, which took place on Saturday evening in Abyan province, targeted an abandoned school that soldiers of the army’s 119th Brigade who were battling the al-Qaida fighters were sheltering in, military and medical officials said.

The school is located just east of Abyan’s provincial capital, Zinjibar, seized in May by Islamic militants taking advantage of Yemen’s political turmoil to expand their reach. In recent days, fighting in the area has been heavy; 28 soldiers and militants were killed there Saturday.

After the airstrike, militants inspecting the site shot and killed soldiers who were wounded by the bombing, the military officials said, speaking on condition of anonymity because they were not authorized to release the information.

Yemen’s turmoil is of deep concern to the United States and Europe in large part because of the possibility that al-Qaida in the Arabian Peninsula will benefit from it and carve out an even bigger haven in Yemen from which to plot attacks on the West.