An attack on a military base in northeast Mauritania by unidentified assailants late Saturday killed 18 soldiers and injured 30, a military source said Sunday. Among those killed were the head of the base, Captain al-Kouri Walid Ahmed, said the source, who spoke to Deutsche Presse-Agentur (dpa) on condition of anonymity. He said the death toll may increase, as some of the injured were in critical condition. The base is located in the northeast of the country near the borders with Algeria and Mali, dpa reported. The source told dpa that some of the attackers spoke classical Arabic, while others spoke the local dialect. Mauritanian officials have kept silent about the incident although several military units have been placed on high alert. The source said military operations might be conducted in the area where the attack took place.