WARDAK, Iraq (Reuters) - Kurdish Peshmerga forces launched a fresh attack on Islamic State (IS) forces early on Sunday as part of a campaign to capture Mosul, the militants’ de facto capital in Iraq, Kurdish officials said.

Kurdish Peshmerga forces fire a rocket toward Islamic State militants on the southeast of Mosul , Iraq, August 14, 2016. REUTERS/Azad Lashkari

The advance began after heavy shelling and air strikes by a United States-led coalition against IS forces, a Reuters correspondent reported from Wardak, 30 km (19 miles) southeast of Mosul. The militants fought back, firing mortars at the advancing troops and detonating at least two car bombs.

A Peshmerga commander said a dozen villages had been taken from the ultra-hardline Sunni militants as Kurdish forces headed toward Gwer, the target of the operation, 40 km (25 miles) southeast of Mosul.

Repairing a bridge that the militants destroyed in Gwer would allow the Peshmerga to open a new front around Mosul. The bridge crosses the Grand Zab river that flows into the Tigris.

IS said in a statement on its Amaq news service that two car bombs driven by suicide fighters were detonated in one of the villages to block advancing Kurdish forces, causing casualties among the Peshmerga.

Authorities in autonomous Kurdistan gave no toll for the fighting, other than confirming the death of a Kurdish TV cameraman and the injury of another journalist.

Clouds of black smoke rose from the scene of fighting and dozens of civilians fled in the direction of Peshmerga lines, brandishing white flags.

The Iraqi army and the Peshmerga forces of the Kurdish self-rule region are gradually taking up positions around Mosul, 400 km (250 miles) north of the capital Baghdad.

It was from Mosul’s Grand Mosque in 2014 that Islamic State leader Abu Bakr al-Baghdadi declared a “caliphate” spanning regions of Iraq and Syria.

BIGGEST CITY IN ISLAMIC STATE HANDS

Mosul is the largest urban center under the militants’ control, and had a pre-war population of nearly 2 million.

Its fall would mark the effective defeat of Islamic State in Iraq, according to Prime Minister Haider al-Abadi, who has said he aims to retake the city this year.

The Iraqi army is trying to close in from the south. In July it captured the Qayyara airfield, 60 km (35 miles) south of Mosul, which is to serve as the main staging post for the anticipated offensive.

The Peshmerga operation on Sunday was “one of many shaping operations that will also increase pressure on ISIL in and around Mosul,” said an official from the Kurdistan Regional Security Council, using another acronym to refer to IS.

“Noose tightening around #ISIL terrorists: #Peshmerga advancing east of #Mosul, #ISF shoring up south near #Qayyara,”tweeted Brett McGurk, the U.S. envoy to the coalition fighting the militant group.

Preparations for the offensive on Mosul are “approaching the final phase,” McGurk told reporters during a visit to Baghdad on Thursday. He said the planning included considerations for humanitarian aid to uprooted civilians.

Once the fighting intensifies around Mosul, up to one million people could be driven from their homes in northern Iraq, posing “a massive humanitarian problem”, the International Committee of the Red Cross forecast last month.More than 3.4 million people have already been forced by conflict to leave their homes across Iraq, taking refuge in areas under control of the government or in the Kurdish region.