Iranian troops have arrived near Fallujah to take part in the imminent offensive to retake the IS-held city, but there are concerns regarding possible sectarian frictions with the Sunni-majority population

Forces from the Iranian Revolutionary Guards Corps and Iraqi Hizballah have arrived in the southern outskirts of the western city of Fallujah as part of preparations for a planned Iraqi government operation to retake the city from Islamic State militants, Iraqi military and tribal sources said on Sunday.This comes as Iraq's army asked residents to prepare to leave the IS-held city, in another possible indication of the start of the planned offensive, dubbed Breaking Terrorism.

The army "is asking the citizens that are still in Fallujah to be prepared to leave the city through secured routes that will be announced later".

The news comes two days after Tehran announced a commander in its Basij Force was killed in a car bomb south-east of Fallujah

IS is preventing civilians from leaving and has threatened to execute those who attempt to flee

Around 60 Revolutionary Guards arrived on Friday and Saturday to the Mazraa military base 5 km from Fallujah, escorted by dozens of Iraqi Hizballah fighters, an officer in the army operations command in Anbar speaking on condition of anonymity told The New Arab.The Iranian troops are armed with advanced weaponry, he said.The news comes two days after Tehran announced a commander in its Basij Force was killed in a car bomb south-east of Fallujah."The participation of Iranian Revolutionary Guards in the battle of Fallujah would have negative repercussions and may lead some of the (Sunni) tribes fighting IS to withdraw, further delaying the liberation of the city," Faleh al-Fadli, security expert, told The New Arab.Several Shia militias of the Popular Mobilisation will also take part in the offensive on the Sunni-majority city, but the Iraqi prime minister has reportedly pledged they would remain outside the city to avoid sectarian frictions.A meeting was held on Saturday night between the prime minister and Anbar province officials to discuss the Fallujah offensive, MP Khaled al-Alwani told The New Arab."(Prime Minister) Abadi told us during the meeting the Popular Mobilisation would remain outside the city in a support capacity," he added, pointing out the offensive is imminent."The meeting discussed broad details of the battle and the roles of security and tribal forces...and also how to secure the more than 50,000 civilians there," he said.IS is reportedly preventing civilians from leaving and has threatened to execute those who attempt to flee. The population of the city, which is encircled by Iraqi forces and Shia militias, is also suffering from the fallout of shortage in basic supplies The city on the Euphrates river 50 km west of the capital had a pre-war population of around 300,000.

Fallujah was the first Iraqi city to fall to IS in January 2014, six months before the group swept through large parts of Iraq and neighbouring Syria.