Clashes between rival groups and heavy gunfire in southern Yemeni city close airport in Aden

Men stranded at the Aden International Airport, wait as heavy gunbattles between a unit of police commandos loyal to longtime autocratic former President Ali Abdullah Saleh and security forces loyal to the current president, erupted in Aden, Yemen, Thursday, March 19, 2015. Forces loyal to Saleh stormed a section of the international airport in the southern port city of Aden on Thursday, triggering heavy gunbattles with security forces loyal to the current president. The fighting forced the closure of the facility and passengers on a flight to Cairo were scuttled off the plane and into the terminal building. (AP Photo/Hamza Hendawi) (The Associated Press)

General view of the Aden International Airport during heavy gunbattles between a unit of police commandos loyal to longtime autocratic former President Ali Abdullah Saleh and security forces loyal to the current president, in Aden, Yemen, Thursday, March 19, 2015. Forces loyal to Saleh stormed a section of the international airport in the southern port city of Aden on Thursday, triggering heavy gunbattles with security forces loyal to the current president. The fighting forced the closure of the facility and passengers on a flight to Cairo were scuttled off the plane and into the terminal building. (AP Photo/Hamza Hendawi) (The Associated Press)

A man stranded at the Aden International Airport, waits as heavy gunbattles between a unit of police commandos loyal to longtime autocratic former President Ali Abdullah Saleh and security forces loyal to the current president, erupted in Aden, Yemen, Thursday, March 19, 2015. Forces loyal to Saleh stormed a section of the international airport in the southern port city of Aden on Thursday, triggering heavy gunbattles with security forces loyal to the current president. The fighting forced the closure of the facility and passengers on a flight to Cairo were scuttled off the plane and into the terminal building. (AP Photo/Hamza Hendawi) (The Associated Press)

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.