Two Somalis are suspected of having carried out a suicide bombing at a restaurant filled with Western military personnel on Saturday that killed three and wounded at least 15 Djibouti's Interior Ministry has said.
Several members of EU naval and civilian maritime security missions were among those wounded in the attack.
"Early indications of the investigations show that the attackers were two suicide bombers of Somali origin; a man and a veiled woman," the Interior Ministry said in a statement.
The ministry did not say if any group planned the bombing, the first of its kind kind in the country.
National security forces took over the restaurant premises and secured the area, the ministry said.
Djibouti, host to a French military base and the only US military base in Africa, shares its southern border with Somalia where al-Shabab is fighting the government.
Al-Shabab is active inside Somalia but has also carried out gun and bomb attacks abroad. Last year, the group killed 67 people at a Kenyan shopping mall.
Spain said three Spanish military airforce personnel attached to an EU naval mission were injured in the attack, one seriously.
Somali troops and AMISOM - comprising troops from Burundi, Uganda, Kenya, Sierra Leone and Ethiopia - drove al-Shabab out of Somalia's capital, Mogadishu, in 2011, but the group still carries out attacks in the city.
On Saturday, al-Shabab figthers attacked the parliament, killing at least 10 people.