"Mosul and Kirkuk have fallen," Major Rumi Nielson-Green told AFP at the Central Command base.

"Coalition forces are inside the cities," she said, adding "they are mostly special operations forces."

Kurdish fighters earlier reached the centre of Mosul, the main northern Iraqi city, where they kept a low profile, an AFP reporter said.

They were seen in the city around 0725 GMT, but an hour later they seemed to have disappeared.

In Kirkuk, captured by Kurdish and US forces, the situation was spiralling out of the control of local Kurdish chiefs and several people were killed amid pillaging and score-settling, the city's Kurdish governor, Rizgarali Hamgam, told AFP.

SPACE.WIRE