Somali Islamist rebels threatened to attack the capitals of the two central African countries that have deployed peacekeeping troops to prop up Somali's transitional government.
The threat followed renewed fighting in Mogadishu on Thursday when insurgents fired on the Somali president's plane and traded mortar and artillery fire with peacekeepers from Uganda and Burundi, killing at least 21 and wounding dozens.
Mortar shells came crashing down on a busy market area in the capital, in one of the worst such incidents in months.
"It was difficult to differentiate who is who among the bodies of mothers killed by the bombardment of Ugandan and Burundi troops," Sheikh Ali Mohamed Hussein, the regional head of the Mogadishu area for the Al-Qaeda-inspired Shebab Islamist group told reporters late Thursday.
"The children of those mothers must divert the war from Mogadishu to the capital of those nations that attacked Somalia," he said. "I hope they will do that."
He accused the Ugandan and Burundi troops of "indiscriminately shelling" areas populated by civilians every time they retaliate to an attack by Shebab.
According to witnesses, yesterday's clashes started when insurgent fighters opened mortar fire on the airport as President Sharif Sheikh Ahmed was flying out of the country for a diplomatic visit.