(CNN) -- Four Yemeni soldiers were killed and more than 20 injured when suspected al Qaeda militants stormed the headquarters of the Army's 2nd Division in the southern Yemeni city of Mukalla on Monday, three local security officials told CNN.
The military headquarters in Mukalla is one of the main military buildings in the province of Hadramaut.
One senior security official told CNN that three dozen militants were disguised as military forces when they attacked the compound using heavy artillery during the morning hours. "The militants are still in control of a building within the headquarters. They are also holding a number of troops hostage, " a senior security official told CNN on condition of anonymity because he is not authorized to talk to media.
The official said that nearly 200 government special forces and military troops are currently involved in the operation. He confirmed that the militants are linked to al Qaeda.
Military helicopters are surrounding the headquarters from three angles, the official said.
A second security official said the attack started when a vehicle exploded at the main entrance of the headquarters, taking down the gate and allowing two other vehicles transporting militants to enter the compound. Two of the killed were stationed at the entrance.
The official added that governmental troops attempted to halt the militants but were outnumbered near the main gate.
At least a dozen of the injured were taken to Ibn Saina Hospital in Mukalla, according to a medical source within the hospital. "Most of the injured are not in serious condition but as of now we have four deaths confirmed," said the medical source, who asked not to be named.
Back in April, President Abdu Rabu Mansour Hadi vowed to continue fighting al Qaeda until they were defeated. Since then, militants have conducted a number of attacks on military compounds and have killed dozens of senior military and intelligence officials.