Kenyan troops are engaged in heavy fighting with the al-Shabab militant group on the coast of southern Somalia, both sides have said.
Al-Shabab spokesmen told news agencies that fierce clashes were under way in the port city of Kismayo.
Kenyan military spokesman Col Cyrus Oguna confirmed to the BBC that parts of Kismayo had been captured and the rest was expected to fall soon.
The Kenyan soldiers are part of the AU's Amisom force, which is trying to wrest control of Somalia for the newly elected, UN-backed president Hassan Sheikh Mohamud.
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Guillier conceded a "severe defeat" defeat to his supporters as the result came in.
The outage struck Hartfield-Jackson Atlanta International Airport at around 1pm local time, stopping all outgoing flights.
It will be a chilly day for many parts with the highest temperatures, about 10 Celsius (50F) in the far northwest.