BAGHDAD, Nov 24, (Agencies): A suicide truck bomb killed about 100 people, most of them Iranian Shi’ite pilgrims, at a petrol station in the city of Hilla 100 kms (62 miles) south of Baghdad on Thursday, police and medical sources said. Islamic State (IS), the ultra hardline Sunni militant group that considers all Shi’ites to be apostates, claimed responsibility the attack in an online statement. The group is also fighting off a US-backed offensive on its stronghold Mosul, in northern Iraq, in which Iranian-trained Shi’ite militias are taking part.The pilgrims were en route back to Iran from the Iraqi Shi’ite holy city of Kerbala, where they had commemorated Arbaeen, the 40th day of mourning for the killing of Imam Hussein, a grandson of the Prophet Muhammad (PBUH), in the 7th century AD, the medical sources said. The gas station has a restaurant in its premises that is popular with travellers.Five pilgrim buses were torched by the force of the blast from the explosives-laden truck, a police official said. Islamic State has intensified attacks over the past month in areas out of its control in efforts to weaken the offensive launched on Oct 17 to retake Mosul, the last major city under IS control in Iraq. Iran’s Foreign Ministry condemned the attack without giving a casualties toll.Tehran will continue to support Iraq’s ‘’relentless fight against terrorism,” ministry spokesman Bahram Qasemi was quoted as saying by Tasnim news agency. Meanwhile, Iraqi forces battled the Islamic State group deep inside Mosul Thursday, piling pressure on jihadists who have no more escape routes but leaving trapped civilians in the crossfire.Elite forces gained new ground in east Mosul, looking for fresh momentum as stifferthan- expected IS resistance threatened to bog down the five-week-old offensive against the jihadists’ last major stronghold in Iraq. Maan al-Saadi, a commander with the Counter-Terrorism Service (CTS), told AFP on the front line in Mosul that his forces were battling IS in the neighbourhood of Al-Khadraa in Iraq’s second city. “They cannot fl ee. They have two choices — give up or die,” he said.Over the past few days, Iraqi forces have cut off the main supply line running from Mosul to the western border with Syria, where IS still controls the city of Raqa. The US-led coalition also bombed bridges over the Tigris river that splits Mosul in two, reducing the jihadists’ ability to resupply the eastern front. An old British-era bridge, which cannot be used by heavy vehicles, is the only one still standing in the city. “The Iraqi advance on the south and southeast of the city has started to pick up some steam, which we think is a really great development,” coalition spokesman Colonel John Dorrian said.“They’re going to have to react to that advance. That thins out their defences,” he said. A senior CTS commander said Wednesday that 40 percent of eastern Mosul had now been retaken. “It is extraordinarily tough fighting, just brutal, but there is an inevitability to it. The Iraqis are going to beat them,” Dorrian told AFP. Iraqi forces launched a major offensive on Oct 17 to retake Mosul, where jihadist supremo Abu Bakr al-Baghdadi proclaimed a caliphate in 2014.They are also edging towards the city from a northern front as well as from the south, where they are within striking distance of Mosul airport. Among the forces deployed south and west of the city are the Hashed al-Shaabi (Popular Mobilisation), an umbrella for paramilitaries dominated by Tehran-backed militias. They have focused their operations on Tal Afar, a large town still held by IS west of Mosul and on Wednesday announced they had cut the main road between it and Syria. That will make it very long and dangerous for IS if it attempts to move fighters and equipment between Mosul and Raqa, the last two bastions of their crumbling “state”.The eastern side of the city was expected to offer less resistance than the west bank but CTS forces have faced a torrid time. IS fighters moving in an intricate network of tunnels have used snipers, booby traps and a seemingly endless supply of suicide car bombers to stop Iraqi forces. The authorities have not released casualty figures since the start of the offensive but fighters have admitted being surprised by how fierce IS resistance has been. The intensity of the fighting has been one of the factors preventing civilians from fleeing to the safety of some of the camps being set up around Mosul.The United Nations had expected around 200,000 people to flee their homes in the first few weeks of the offensive, but only about a third of that number have been displaced so far. The International Organization for Migration said Thursday that around 76,000 people had been displaced since Oct 17. It said that about 7,000 people had already returned to their homes, leaving roughly 69,000 still displaced, most of them in camps. Forces have so far encouraged residents to remain in their homes as they inched through the city, fighting house-to-house. Evacuating the population would allow Iraqi forces to use heavier artillery and achieve faster results but Iraq’s leadership wants to prevent the complete destruction of Mosul.