Armed militants linked to al-Qaeda stormed a Yemeni military base in a restive southern province before dawn Monday, killing at least 20 soldiers and capturing more than two dozen others, according to Yemeni military officials. The assault occurred hours after a U.S. drone strike reportedly killed a top al-Qaeda figure involved in the 2000 bombing of the USS Cole in Yemen.

The attack on the base was the latest indication of an intensifying conflict between U.S.-backed Yemeni security forces and al-Qaeda’s Yemeni affiliate for control of southern Yemen. Over the past year, the militants have seized large swaths of territory in the south, taking advantage of political turmoil during Yemen’s populist revolution, which ousted longtime authoritarian ruler Ali Abdullah Saleh.

Since President Abed Rabbo Mansour Hadi took office in February, officially ending Saleh’s rule, the militants have escalated their assaults, staging raids and suicide bombings. The government has responded with airstrikes, while the Obama administration has increased its use of drones to assassinate militants in the area.

It was unclear whether Monday’s assault was in retaliation for the death of Fahd al-Quso, a senior leader of al-Qaeda in the Arabian Peninsula, or AQAP, the Yemeni affiliate of the terrorist network. Yemeni government officials said Quso and another man were killed in an attack Sunday in the southern province of Shabwa while he was stepping out of his car. Quso, 37, was on the FBI’s most-wanted list. He was indicted in connection with the suicide attack on the destroyer USS Cole, in which 17 American sailors were killed and 39 were injured in the southern port of Aden.

Monday’s attack unfolded at a military base on the outskirts of Zinjibar, the capital of Abyan province, which is the nexus of the current battles. There were differing estimates of the toll, with some news agencies reporting as many as 32 killed. A spokesman for Ansar al-Sharia, a group linked to AQAP, told the Reuters news agency that the militants had captured 28 soldiers and a tank. He did not say whether the assault was meant to avenge Quso’s death.

This file photo released by the FBI in 2003 shows Fahd al-Quso, who was charged as an al-Qaeda member who helped to plan the attack on the USS Cole that killed 17 American sailors in 2000. (FBI, File/Associated Press)

In his first public speech, Hadi declared Saturday that the government’s fight against al-Qaeda was in its early stages and that he would improve Yemen’s counterterrorism cooperation with the United States. The Obama administration played a key diplomatic role in ushering Saleh from power and replacing him with Hadi.