SANAA, Yemen -- A Yemeni army commander says Shiite Houthi rebels have seized the presidential palace in the capital, Sanaa, a move he described as a "coup." Col. Saleh al-Jamalani, the commander of the Presidential Protection Force that guards embattled President Abed Rabbo Mansour Hadi, says the rebels swept into the presidential palace on Tuesday afternoon. He told The Associated Press that the rebels were aided by insiders and are looting arm depots on the palace grounds. Yemen's information minister said the Houthi rebels were shelling the president's house. Hadi was not at the presidential palace during the takeover but at his residence. In New York, the U.N. was set to hold an emergency session on the situation in Yemen. On Monday, a cease-fire halted intense clashes near the presidential palace after the rebels seized control of state-run media. The fighting, centered on the palace and a military area south of it, marked the biggest challenge yet to Hadi by the Houthis, who swept down from their northern strongholds last year and captured the capital in September. The violence has plunged the Arab world's poorest country further into chaos and could complicate U.S. efforts to battle al Qaeda's Yemeni affiliate, which claimed responsibility for the attack on a Paris satirical magazine this month and which Washington has long viewed as the global network's most dangerous branch. The Houthis are seen by their critics as a proxy of Shiite Iran -- charges they deny -- and are believed to be allied with former President Ali Abdullah Saleh, ousted in a 2012 deal after Arab Spring protests. They have vowed to eradicate al Qaeda and have battled the group, but are also hostile to the U.S. Their official slogan is "Death to Israel. Death to America." A State Department spokesperson told CBS News correspondent Margaret Brennan on Monday that the U.S. is monitoring the situation closely and "will calibrate the embassy security posture accordingly."