Colonel Khathar Sheikhan of the Kurdish forces, known as peshmerga, confirmed on Tuesday that having acheived their objectives, his troops "are just holding our positions" in the Khazer area.

The pause came after a day of intense fighting involving airstrikes, heavy artillery and IS car bombs.

The Iraqi security forces and Kurdish peshmerga fighters, backed by US air and ground support began the battle to take back Mosul on Monday. Mosul is Iraq's second largest city and the IS group's last urban bastion. The front line east of Mosul is some 30 kilometers (20 miles) from the city.

The operation is expected to take weeks or even months. French Defence Minister Jean-Yves Le Drian warned reporters on Tuesday: "It could be a long battle, it's not a blitzkrieg... It's a lengthy affair."

On the first day, however, Pentagon press secretary Peter Cook said that Iraqi forces were "ahead of schedule."

The White House said Iraqi forces have taken the leading role in this operation, with US troops in Iraq serving to train, advise and assist Iraqis.

Obama confident of success

Ahead of a state dinner with Italian Prime Minister Matteo Renzi, US President Barack Obama said that the coalition "continues to be relentless against IS on all fronts."

"Even if this continues to be a very difficult battle, I am confident that we will win and IS will lose," he told Italian daily "La Repubblica."

EU's security commissioner Julian King warned, however, that Europe must be prepared for a new influx of Islamic State jihadists if Iraqi forces succeed in retaking Mosul.

"The retaking of the IS' northern Iraq stronghold, Mosul, may lead to the return of violent IS fighters to Europe," he told German paper "Die Welt."

Even a handful of jihadists returning would pose a "serious threat that we must prepare ourselves for," King added.

IS stronghold

Retaking the city would be a major blow to IS, which overran much of the country after seizing Mosul in June 2014 from a fleeing Iraqi army. The jihadists captured tanks, weapons, ammunition and money to fuel their subsequent operations.

The long-awaited offensive to recapture Iraq's second-biggest city follows months of preparations after security forces pushed the Sunni extremist group from central Iraq over the past year.

Conquering Mosul would pave the way for an assault on what would be the last IS stronghold in Syria, the town of Raqa. French Foreign Minister Jean-Marc Ayrault said on Tuesday that the international coalition had a "responsibility" to retake the city, adding that not going on to Raqa "would be a bad mistake."

Protests against Turkish troops

As the operation pushed on on Tuesday, thousands of Iraqis gathered outside the Turkish embassy in Baghdad, protesting against Ankara's military presence north of Mosul, despite demands by the government for Ankara's soldiers to leave.

Protesters carried Iraqi flags and demanded that the Turks withdraw from Bashiqa base, in line with repeated requests by Iraqi Prime Minister Haider al-Abadi.

"Out out, you occupier," was one of the slogans being chanted, according to witnesses.

Turkey, which has close relations with the Iraqi Kurds, is not part of the operation to retake Mosul. Turkish President Recep Tayyip Erdogan has repeatedly insisted that his country participates, however, insisting that the troops - which include about 150 soldiers deployed in Iraq last year to train Sunni forces - are part of Turkey's self-defense.

Turkey's Prime Minister confirmed on Tuesday that Turkish fighter jets have been involved in airstrikes alongside the US-backed coalition.

ksb/jm (AFP, Reuters, dpa)