Yemeni officials said Sunday a government plane has mistakenly bombed a building in a southern region of the country, killing at least 20 Yemeni soldiers.

The Associated Press says the soldiers had taken shelter in the abandoned school building.

Details of the deadly incident Saturday are still not clear.

The French news agency reports al-Qaida militants attacked the school after the air strike, killing more soldiers. And Reuters news agency quotes a Defense Ministry official as denying that Yemeni soldiers were killed in an accidental bombing.

Other authorities say the bombing happened near the volatile city of Zinjibar. Security forces have been trying to regain control of the city for months.