U.S. President Obama said the action was necessary to prevent the oil-rich African giant from falling further into chaos.
Somali insurgents say they shot down a U.S. drone aircraft flying over the southern port of Kismayu on Monday.
Two kidnapped aid workers were released on Sunday in Darfur after more than 100 days in captivity.
Zimbabwe's MDC said it would boycott the country's unity government until sticking points have been resolved.
Somali pirates demanded $4 million in ransom plus the release of the two hijackers captured by the Spanish Navy on Oct. 4.
A Zimbabwean court ordered the detention of Roy Bennett, a senior official in Prime Minister Morgan Tsvangirai's MDC party.
A Zimbabwe court ordered prison for Roy Bennett, a senior official in PM Morgan Tsvangirai's MDC party.
Somalia's two main insurgent groups agreed to a truce on Wednesday to end days of clashes between them.
Uganda has freed Somalia's state minister for defence after his arrest and questioning by security officials.
Gunmen kidnapped Somalia's state minister for defense during a visit to Uganda in the capital Kampala.