At least two security officers have been killed after two blasts struck a busy restaurant in downtown Djibouti, police said.

The blasts at La Chaumiere restaurant, popular with Western tourists, wounded 11 other people according to Reuters news agency.

"It's a criminal act. We have two people dead and 11 wounded. It was grenades," Colonel Omar Hassan, head of police in Djibouti city, told Reuters.

The French foreign ministry confirmed that several of its nationals were slightly wounded in the attack, and the Netherlands' De Telegraaf reported that six Dutch soldiers who had been taking part in an anti-piracy mission were also lightly wounded.

Djibouti has the United States' only military base in Africa, where drones are operated from. Earlier this month the US signed a $63m a year 10-year lease for the base knowns as Camp Lemonnier.

The tiny East African country has also contributed troops to the African Union Mission in Somalia.

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.

In a statement on Twitter, Djibouti's Finance Minister Ilyas M. Dawaleh said the country must "remain united in the face of such barbaric acts".