Al-Shabab militants in Somalia have begun making their own explosives, according to documents seen by the Reuters news agency.
A confidential UN report links the development of homemade explosives by the Islamist extremists to an increase in bombings in the Somali capital, Mogadishu.
The claim is based on analysis by a panel of experts of samples taken following 20 attacks.
The UN has not commented on the report.
Since September, there have been at least 19 car- or truck-bomb attacks by al-Shabab in which five people or more have died.