Witnesses say that hundreds of gun-toting al-Shabab fighters have moved back into central Somali towns abandoned over the last week by Ethiopian troops. Ali Muhyadin, a resident in the town of El-bur, said Tuesday that residents woke up on Sunday and found that Ethiopian troops had abandoned their bases.

Residents said al-Shabab fighters then beheaded two men accused of collaborating with the Ethiopians and dumped their headless bodies in town.

Al-Shabab was reported to have returned to two other towns - Mahas and Wabho - after Ethiopian troops left.

Ethiopia's president recently promised that Ethiopian forces would leave Somalia soon. Ethiopian forces still occupy the larger towns of Baidoa and Beledweyne.