The United Nations warned Monday of an increased threat of attacks from Somalia's Al-Qaeda-linked Shebab as a major offensive launched against them this month gathers pace.
"Coinciding with the offensive and even ahead of it, Al-Shebab have become more active," UN envoy to Somalia, Nicholas Kay, told AFP.
"They feel threatened and endangered, and so they have carried out significantly more terrorist attacks in Mogadishu in the last couple of months."
UN-mandated African Union troops have been battling Shebab militants in Somalia since 2007, but earlier this month launched a fresh offensive, fighting alongside Somali government forces.
Kay said the operation is pushing the rebels out of key bases, which could prompt them to stage attacks in Mogadishu, as well as other countries in the region such as Uganda and Kenya.
Security sources report some Shebab members are fleeing to mountains in northern Somalia's Puntland region, but some foreign fighters may seek to cross to Yemen, or flee southwards into neighbouring Ethiopia and Kenya.
"They're fleeing into the bigger cities, there are more of them entering Mogadishu," Kay added.
"Some of them are looking to flee perhaps the country and are heading to the remoter corners," he said, speaking after an AU peace and security council meeting in the Ethiopian capital.
Shebab gunmen have largely fled ahead of the AU advance, only to later stage guerrilla attacks.
But the Islamists have also vowed to retaliate against the troop-contributing nations, with soldiers in the 21,000-strong force coming from Burundi, Djibouti, Ethiopia, Kenya, Sierra Leone and Uganda.