ferocious battle with Islamic State fighters in northern Iraq is being treated as a warning of more to come.
ficials were caught off guard by the brazen attack, as militants stormed Kirkuk in the early hours of Friday, killing around 100 people. Reuters in the Iraqi city of Erbil says the tactics were reminiscent of last year's carnage in Paris.
>> This large group, up to 100 fighters, were dropped off on the southern perimeter of the city. Then they scattered out to specific strategic targets with a lot of heavy machine guns, regular machine guns, RPGs, and suicide vests.
The jihadists appear to be highly trained for urban combat, which may signal trouble as Iran tries to push Islamic State out of its second biggest city, Mosul.
>> A very tough and long drawn out battle can be expected if they dig in and fight as they did in Kirkuk. And particularly, in Mosul they've had up to two years now to prepare defenses, we're hearing that they've put explosives all over the city, they've got trenches that they've filled with oil.
So essentially, many people we talked to said that it does indicate that it would be a much tougher fight in Mosul than perhaps they've expected.
Iraqi and Kurdish forces backed by the United States have so far cleared dozens of villages around Mosul, but have yet to move on the city itself.