Bahrain Mirror (Reuters): Iraqi government forces fought Islamic State militants near Falluja on Monday and bombarded central districts at the outset of an offensive to retake the longtime jihadist stronghold on the western approaches to the capital Baghdad.

Some of the first direct clashes occurred in al-Hayakil area on Falluja's southern outskirts, a resident said. Iraqi troops also approached the northern suburb of Garma, the top municipal official there said, to clear out militants before turning their attention toward the city center.

Airstrikes and mortar salvoes overnight targeted neighborhoods inside the city proper where Islamic State is believed to maintain its headquarters, but the bombardment had eased by daybreak.

Iraqi military spokesman Brigadier General Yahya Rasool, speaking on state television, described the government's advance as "careful" and reliant on engineers to dismantle roadside bombs planted by the militants.

Falluja, a longtime bastion of Sunni Muslim jihadists 50 km (30 miles) from Baghdad, was the first city to fall to Islamic State, in January 2014. Six months later, the group declared a caliphate spanning large parts of Iraq and neighboring Syria.

Iraqi forces have surrounded Falluja since last year but focused most combat operations on IS-held territories further west and north. The authorities have pledged to retake Mosul, the north's biggest city, this year in keeping with a U.S. plan to oust IS from their de facto capitals in Iraq and Syria.

But the Falluja operation, which is not considered a military prerequisite for advancing on Mosul, could push back that timeline. Two offensives by U.S. forces against al Qaeda insurgents in Falluja in 2004 each lasted about a month and wrecked significant portions of the city.

There are currently between 500 and 700 IS militants in Falluja, according to a recent U.S. military estimate.