In the early morning, ISIS attempted to blow up a power station on the outskirts of Kirkuk as well as a police headquarters building. The attackers, said to be about a dozen in number, killed six Kurdish police officers and 13 power company workers. Although unconfirmed at this time, images obtained by SOFREP appear to indicate that the Jihadists used suicide bombers, a tactic that the Kurds are all too used to seeing from ISIS.
The Kirkuk strike appears to be a counter-attack in response to the coalition (which includes Kurdish Peshmerga) advance on Mosul. Near Kirkuk is Hawija, a traditional hotspot for Jihadi activity going back over a decade, which is still under ISIS control today. More than likely, this is where the ISIS fighters and suicide bombers infiltrated the city from. Najmiddin Karim, the governor of Kirkuk blamed the attack on sleeper cells but given the long Jihadi beards seen on terrorists in multiple photos, it seems unlikely that they had been moving around the Kurdish held city unimpeded for long.
Other reports state that the ISIS fighters asked to be taken to the Iranians employed at the power station and specifically killed them. The power plant was built by an Iranian company. This would give the appearance that the Jihadists also wanted to send a message to Iran. Iranian proxy forces in the form of Shia militias are also fighting for control of Mosul.