Islamic militants have advanced further into Iraq after taking control of the country’s second largest city, Mosul, earlier this week in a devastating show of strength against the Baghdad government.

Early Wednesday, the Islamic State in Iraq and the Levant (ISIL) took control of several areas in the Hawija district of Kirkuk province before being pushed back by police and army troops.

The insurgents are also reported to have taken over several parts of Tikrit.

Heavy clashes were reported in the downtown area with an unknown number of militants fighting security forces near the Salaheddin provincial government offices.

The town of Beiji had also been seized before being recaptured by the army. Iraq’s Interior Ministry said the extremists destroyed several buildings including the court house and a police station. They’re also reported to have taken army weapons caches. Later they surrounded a local oil refinery.

The Islamic State of Iraq and the Levant militants are now in control in much of western and central Iraq as well as eastern Syria.