Washington — Just two days after the US forces killed a top Islamic State commander Abu Sayyaf in a ground operation in Syria, the ISIS has begun to wreak havoc in Iraq.

In the biggest gain for the extremists this year, key Iraqi city of Ramadi which is capital of Anbar province (Iraq’s Sunni heartland) fell to the Islamic State as Iraqi forces reportedly fled the area, leaving behind vehicles and weapons.

It is apparently an inglorious reminder of last summer, when the ISIS had launched a fierce assault on a huge swathe of Iraq, taking over the city of Mosul as the forces had run for their lives, shunning their military weapons and some even their uniforms, Zee News reported.

The ISIS used a series of suicide car bombings and staged mass killings of not only soldiers but Iraqi civilians. Some 500 (including civilians) have been reportedly killed and 8000 were forced to flee, a spokesperson for the governor of Iraq’s Anbar province told a news agency.

“We estimate that 500 people have been killed, both civilians and military, and approximately 8,000 have fled the city.”

US Secretary of State John Kerry has meanwhile assured that the situation in Ramadi will be “reversed” in weeks as troops will be re-deployed, Reuters reported.

Kerry was speaking to a news conference in Seoul and confirmed that Ramadi had been a target of opportunity for the Islamist militants.

Earlier, the Pentagon had refused to accept that the city has fallen to the ISIS completely, calling the situation “fluid and contested”, reported the AFP.

“We`re continuing to monitor reports of tough fighting in Ramadi and the situation remains,” Pentagon spokeswoman Maureen Schumann told AFP.

The BBC and CNN have quoted senior government officials as confirming the fall of Ramadi.

Iraq is gearing up to send troops to the besieged city of Ramadi

Recently, reports about killing of the top ISIS commanders (including chief Abu Bakr al-Baghdadi and no. 2 in ISIS Abu Alaa al-Afri) had come as huge setbacks for the extremist groups, but with the takeover of Ramadi, the ISIS is seeking to spring back to prominence.

The BBC quoted a top source in Anbar governor’s office as saying that Ramadi was now under the full control of Islamic State, and all government troops had withdrawn.

Iraq is however preparing to send forces soon to Ramadi to recapture the city, tweeted a CNN journalist Rosemary Church.

Iraqi PM has also urged the security forces not to abandon their positions in Anbar province.