Kenya's military says African Union forces have taken control of parts of Kismayo, the last major Islamist militant bastion in southern Somalia, in an assault from the beach.
The port city has been a stronghold of the al-Qaeda-aligned group al-Shabab.
Al-Shabab spokesmen told news agencies fierce fighting is under way.
The Kenyan troops are part of the AU's Amisom force, which is trying to wrest control of the country for the newly elected United Nations-backed president.
Kenyan military spokesperson Colonel Cyrus Oguna confirmed to the BBC that parts of Kismayo had been captured and the rest was expected to fall soon.
He says some parts of the city are still under the control of al-Shabab, "because we only got there a couple of hours ago, and Kismayo is a big city".