Three of Africa's most dangerous Islamist militant groups are striving to coordinate their operations and represent a deepening threat to security on the continent, the US has warned.
General Carter Ham, head of US military's Africa Command, said there were signs that Boko Haram in Nigeria, al-Shabaab in Somalia and al-Qaida in the Islamic Maghreb were sharing money and explosive materials and training fighters together.
"Each of those three organisations is by itself a dangerous and worrisome threat," Ham told an African Centre for Strategic Studies seminar in Washington. "What really concerns me is the indications that the three organisations are seeking to coordinate and synchronise their efforts - in other words, to establish a cooperative effort amongst the three most violent organisations … And I think that's a real problem for us and for African security in general."
Al-Shabaab is active in Somalia and has been blamed for attacks in Kenya. Last year, the group, which is allied to al-Qaeda, claimed responsibility for the death of Somali interior minister Abdi Shakur Sheikh Hassan. It has, however, suffered setbacks in recent months.
Last month, the US classified three of the alleged leaders of Boko Haram, an Islamist sect based in north-east Nigeria, as "foreign terrorists", but it declined to blacklist the organisation to avoid boosting the group's profile internationally.
Al-Qaida in the Islamic Maghreb (AQIM), an affiliate of al-Qaida based in north Africa, is mainly a criminal organisation operating in the Sahel region. It kidnaps westerners for ransom and fuels Africa's drug trade, according to intelligence officials.
US officials fear that a power vacuum in northern Mali after a military coup in March may open an expanded area of operations for Islamist militants.
Ham, addressing senior military and civilian officials from Africa, the US and Europe, said AQIM was operating "essentially unconstrained" throughout a large portion of northern Mali, where Islamists have imposed an extreme version of sharia law.
He added: "The linkages between AQIM and Boko Haram are probably the most worrisome in terms of the indications we have that they are likely sharing funds, training and explosive materials."