NAIROBI, Kenya (AP) - Will the allure of a US$5 million (S$6.3 million) reward be the downfall of a tweeting, rapping American jihadi who once fought alongside the Somali militant group al-Shabab but now denounces their methods and motivations in online feuds?

A US State Department official said Thursday that the US$5 million reward offered for Omar Hammami could exploit what are believed to be fault lines between Somali groups that may be for and against Hammami.

The Alabama-born American was once high in the ranks of al-Shababab but has since had a falling out with the group's leader.

The US announced on Wednesday the US$5 million reward for information leading to the arrest of Hammami and another US$5 million reward for a second American fighting in Somalia, Jehad Mostafa.