The former French colony's port is also used by foreign navies protecting the Gulf of Aden's shipping lanes, some of the busiest in the world, from Somali pirates.
It has also contributed troops to the African Union Mission in Somalia. Other contributing countries, Kenya and Uganda, have in the past been hit by gun and bomb attacks by Somalia's al Qaeda-linked Shabaab insurgents.
Somali troops and AMISOM, comprising troops from Uganda, Kenya, Burundi and Djibouti, drove al Shabaab out of Somalia's capital, Mogadishu, in 2011.
On Saturday, al Shabaab attacked the parliament in Somalia, killing at least 10 security officers.