Kenyan army spokesman Col Cyrus Oguna said a joint operation of Kenyan and Somali government troops was launched overnight and was "basically amphibious".
"We cannot give casualty figures at the moment, the damage has not been assessed, but I can tell you our forces are already in Kismayo."
More top news
The Serious Fraud Office has been fined £180k after confidential documents from a high-profile investigation were sent to the wrong person.
British hopes for a sunny Easter break have been dealt a blow with forecasters warning of a week of wind, rain and even snow.
More than one in five school staff have had a false allegation made against them by a pupil, according to a survey.