Islamic State has accused Somalia's al Qaida affiliate of killing several jihadi leaders who defected to its side, including a Sudanese man sentenced to death for killing a US diplomat and his driver in Khartoum.
A detailed report on two IS-affiliated websites said al-Shabab leaders ordered the killing and detention of dozens of jihadis who expressed their willingness to join IS.
They include Mohamed Makawi, a Sudanese who took part in the drive-by shooting of John Granville and his driver in the Sudanese capital on January 1 2008.
Makawi and an accomplice, Abdelbasit Haj Hamad, were among four sentenced to death in Sudan for killing Mr Granville but escaped from prison in 2010.
The US offered up to 10 million dollars for information leading to the capture of the two men.