Heavy fighting between rival groups in southern Yemen has forced the closure of the international airport in the city of Aden.

Airport officials say the fighting, which erupted early on Thursday morning, is between forces loyal to the former Yemeni president and militiamen loyal to current President Abed Rabbo Mansour Hadi, who is based in Aden.

More than a 100 passengers who had boarded a flight to Cairo, including an Associated Press reporter, were ordered off the Yemenia aircraft and made their way to the terminal.

The sound of heavy explosions shook the terminal building as the clashes intensified.

The security and aviation officials say at least two shells have hit the airport's grounds. They spoke on condition of anonymity because they were not authorized to talk to reporters.