Story highlights Official says estimated number of attackers is between 10 and 15

An Al-Shabaab spokesman says the attack killed Kenyan Christians

The attack targeted a compound in Mandera County that primarily housed quarry workers

Nairobi, Kenya (CNN) Al-Shabaab claimed responsibility Tuesday for a nighttime attack on two homes in northeastern Kenya's Mandera County.

The attack killed at least 14 people and injured 11 others, according to Mandera County Commissioner Alex Nkoyo.

The compound housed primarily quarry workers.

The attack began around 1 a.m. when a group of men using a variety of weapons attacked the compound, Nkoyo told CNN.

The commissioner said an explosive device -- something other than a hand grenade -- was used to blow open a gate to the compound. The attackers then entered and started shooting.

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