(Adds Houthi statement in paragraph 13)Dec 16 (Reuters) - Two major freight firms including MSC, the world's biggest container shipping line, on Saturday said they would avoid the Suez Canal as Houthi militants in Yemen stepped up their assaults on commercial vessels in the Red Sea. The Liberian-flagged MSC Palatium III was attacked on Friday with a drone in the Bab al-Mandab Strait off Yemen, at the southern end of the Red Sea, according to the Houthis. No injuries were reported, but the vessel suffered some fire damage and was taken out of service, MSC said in a statement. U.S. Central Command said the guided-missile destroyer Carney had shot down 14 drones launched by the Houthis in the Red Sea on Saturday morning. The rise in Red Sea war risk premiums translates into tens of thousands of dollars of extra costs for a seven-day voyage.