Wael Qubady, Associated Press
In this photo taken on Monday, Aug. 3, 2015, fighters against Shiite rebels known as Houthis stand on their armored vehicles on a road leading to Al-Anad base near Aden in the southern province of Lahej, Yemen.

SANAA, Yemen — Yemen's al-Qaida branch has exploited the chaos in this embattled country to capture three towns near the southern port city of Aden where pro-government forces have been advancing against Shiite rebels in recent weeks, officials said Thursday.

According to witnesses, al-Qaida's black banners were raised over buildings in the towns of Rabat, al-Lahoum and al-Masaabin. Security officials said the extremist group seized government buildings without a fight and turned them into military bases.

Upon entering al-Lahoum, al-Qaida fighters demolished a building after accusing its owner of being an agent for Yemen's former President Ali Abdullah Saleh and his allies, the Shiite rebels known as Houthis, the officials also said. They spoke on condition of anonymity under regulations while the witnesses did not want to be identified, fearing reprisals.

Yemen's armed forces have splintered over the conflict with the Shiite rebels, creating a security vacuum in some parts of the impoverished country that allowed the local al-Qaida branch to capture territory.

Meanwhile, a plane belonging to Yemenia, the national carrier, landed in Aden with 150 Yemenis who had fled to Djibouti when the fighting intensified in March, airport officials there said. It was the first commercial use of Aden's airport since Saudi-led airstrikes began in late March, targeting the rebels and their allies.

Airport chief Tarek Abdu Ali said Thursday's flight would be followed by daily flights to Aden. Sanaa's airport will also receive daily flights from the Jordanian capital, Amman, according to the civil Aviation Authority.

Yemen's International Committee of the Red Cross said it has flown back seven Houthi prisoners from Aden to the country's rebel-held capital, Sanaa. The flight was allowed through as part of an agreement to exchange prisoners between the pro-government and rebel commanders, Yemen's ICRC spokesman Shahin Ammane said.

The fighting in Yemen pits the Houthis and troops loyal to former President Ali Abdullah Saleh against southern separatists, local and tribal militias, Sunni Islamic militants and loyalists of exiled President Abed Rabbo Mansour Hadi. After months of fierce fighting, pro-government forces recently routed the rebels from Aden and have since been pushing north of the coastal city.