A car bomb on Thursday in a normally quiet Mogadishu neighborhood blew the facade off a tea shop where intelligence officers are known to congregate, killing at least 11 people, police said.

A ball of smoke rose into the sky, as survivors ducked for cover. Police Capt. Mohammed Hussein said he saw 11 bodies. The tea shop is frequented by members of Somalia’s intelligence unit but it wasn’t immediately known how many of the victims were government employees.

The al-Qaida-linked group al-Shabab has increased the frequency of attacks in Somalia’s capital in recent weeks, raising the specter of a return to daily violence. Last week an al-Shabab team attacked the presidential palace with two car bombs and seven gunmen. A car bomb exploded near a U.N. convoy earlier this month.

Witnesses said the car bomb sped toward the tea shop before detonating. Broken tea glasses were scattered on the ground amid splatters of blood.

After controlling most of Mogadishu for years, al-Shabab was pushed out by African Union forces in August 2011, allowing an era of relative peace to be ushered in. However, al-Shabab has increased its pace of attacks in recent weeks, including the use of mortar fire attacks, complex suicide team attacks and even targeted murders.

Gunmen shot dead a health worker giving out polio vaccinations on Wednesday night, the second polio worker killed in the capital this week, police said.

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