Big explosions followed by gunfire have been heard near the main entrance of the airport in the Somali capital, Mogadishu, local media have reported.
Thick smoke could be seen rising from the area, where there is also a base for African Union (AU) peacekeepers.
Local journalists said the blasts had been caused by two bombs. At least one was detonated by a suicide attacker in a vehicle near a checkpoint, they said.
There are reports of casualties among security guards on the checkpoint.
The militant Islamist group, al-Shabab, which is allied to al-Qaeda, has carried out frequent attacks in Somalia, including in Mogadishu, in an attempt to oust the UN-backed government.
The group has been pushed out of most of the main towns it once controlled, but analysts say it remains a potent threat.
It has been increasing its attacks ahead of planned elections in Somalia.
Hotels have been attacked by car bombs and then armed assault teams over the past few weeks.
The large airport area in Mogadishu is a secure “green zone” for UN operations, the AU peacekeeping force and foreign embassies.
The Somali government, with the help of African Union forces, is fighting al-Shabab militants in several parts of the country.