Kenya said Saturday that airstrikes have killed at least 60 al-Qaida-linked militants in southern Somalia, as part of an ongoing effort to force them out of the country.

A military spokesman told reporters that al-Shabab militants were killed in Friday's airstrikes in the town of Garbaharey in Somalia's Gedo area. He said the military was tipped off about the militants' whereabouts, and that he expects the death toll from the attack to rise.

In a related development, Britain said Saturday that London believes there is a heightened terrorist threat in Kenya. A Foreign Office statement says Britain believes terrorists may be “in the final stages of planning attacks.”

The statement warns that terrorist attacks may be indiscriminate and could target places frequented by expatriates and tourists.

Somalian media reported Saturday that al-Shabab forces had withdrawn from Buurdhuubo District of Gedo Region in southwestern Somalia. The reports quote witnesses as saying that insurgents carrying weapons moved out of the area together with their armored vehicles. Reports also say that transitional government troops backed by Kenyan forces have advanced to the area.

Also Saturday, international aid group Doctors Without Borders made a renewed call for the safe release of two Spanish workers who were kidnapped in Somalia in October. The Swiss-based group is currently considering whether to continue its humanitarian work in Somalia, one of the world's most dangerous places for humanitarian workers.

Al-Shabab is known for enforcing a strict brand of Islam in the areas under its rule. The group has blocked most international aid workers from accessing parts of Somalia suffering from drought and famine. Kenya has accused it of kidnappings of foreigners on its soil.

Kenyan forces entered Somalia in October to push back al-Shabab, which controls large sections of southern and central Somalia, and is blamed by Kenya for a series of cross-border kidnappings.