Gunmen loyal to ousted Yemeni president Ali Abdullah Saleh blasted buildings at the country's main airport with anti-aircraft guns Saturday, forcing authorities to shut it down, an airport official said. Armed tribesmen and troops in uniform driving pickup trucks mounted with heavy weapons opened fire on a tower and destroyed it, he said. Then they surrounded the airport at the capital Sana'a, cut roads and sent passengers' vehicles away. Authorities canceled flights, the official said. The attack comes a day after Yemen's new President Abed Rabbo Mansour Hadi fired key security officials appointed by Saleh including his half brother, the Air Force commander Mohammed Saleh Al-Ahmar, and his nephew, Tariq, who headed the Presidential Guard. The siege of the airport highlights the challenges faced by Hadi, who has pledged to purge Saleh's loyalists from the army, the security apparatus and key government posts. Saleh stepped down in February after many false starts and reversals by finally signing a power-transfer deal backed by Washington and Gulf Arab states that gave him immunity from prosecution. Critics of the deal say it gave Saleh the ability to act as a president from behind the scenes and plot his comeback, possibly by sowing instability. On Thursday, Yemeni Defense Minister Mohammed Nasser Ahmed told parliament that Saleh is still giving orders to governors and security officials using the headquarters of his son, Ahmed — the commander of the powerful Republican Guards— as his operation room. The airport attack suggests that removing the commanders comes with its own set of dangers — if it is even possible. Aides to sacked Al-Ahmar who held his post for more than 20 years say he will remain in the position and will not follow orders until Hadi also fires some of the ex-president's opponents. His replacement is former Air Force commander Rashid Al-Hanad. They referred to Gen. Ali Mohsen Al-Ahmar, who defected last year to the mass uprising that called for Saleh's ouster and brought his First Armored Division to protect protesters. Also on Friday, Hadi sacked longtime Saleh loyalist Mohammed Ali Mohsen, the head of the Military's Eastern Command, which is responsible for areas where Al-Qaeda is active. He was transferred to an administrative post. The changes however did not touch the ex-president's son Ahmed who kept command of the well-equipped Republican Guard, or his nephew, Yahia, the head of the Central Security Forces. On Tuesday, Saleh's son carried out internal reshuffles of his own, including appointing the now-ousted Presidential Guards' commander Tariq Saleh as a commander of one of the biggest brigades in the Republican Guards. The appointments were reported by state TV even though Hadi's aides said the president had never approved them.