US-backed Syrian forces are engaged in heavy fighting in northeastern Syria after launching a final push against the last territory held by ISIS, with the Syrian Democratic Forces (SDF) spokesman saying the battle could be finished within days. ISIS once controlled swathes of territory across Iraq and Syria that straddled their shared border and stretched over more than a third of both countries. But the group's control of land has since been reduced to a paltry pocket in eastern Deir Ezzor province that the SDF estimates to be only four square kilometres in size.<br/> The Kurdish-led coalition of fighters announced an offensive on Saturday to retake Upper Baghuz, a tiny hamlet on the eastern bank of the Euphrates river close to the Iraqi border, after delaying the operation for a week to allow tens of thousands of civilians to evacuate the town. “Village of Baghuz, which is the only remaining #ISIS pocket, will be cleared soon,” SDF spokesman Mustafa Bali wrote on Twitter. "This battle will be sealed in the coming days," he told Agence France-Presse news agency, adding that his men were so close to ISIS fighters as to be practically “face to face”. Intense gun battles were reported on Sunday morning as the SDF advanced on the northern and western fronts of the town, capturing 41 ISIS positions. The US-backed fighters foiled an ISIS counter-attack at around 4.00am local time, according to Mr Bali, who said "heavy fighting" was taking place inside the last village. Baghuz is all that is left of the “Hajin pocket” in the Euphrates River valley – itself the rump of the “caliphate” declared by ISIS in 2014. The SDF have been advancing on the area since launching a final offensive in December. Remaining in an area of fields and farmhouses less than a few square kilometres are up to 600 ISIS fighters and their families, many of them foreigners. SDF fighters are advancing with support from coalition air strikes and artillery located across the border in Iraq. In the past four months, French howitzer gunners have fired some 3,500 shells over the border, according to the French military. French Defence Minister Florence Parly visited the French gunners at Task Force Wagram Site in Al Qaim in Iraq’s Anbar on Saturday, just 10 kilometres from the ongoing fighting in Syria, to declare that “the end is near”. "The terrorists are leaderless, without communications, in disarray, on the verge of collapse. So let's finish off this fight," she told a group of about 40 French troops stationed at the outpost alongside 100 American soldiers. Across the border in Syria, US special forces remain to “advise and assist” the SDF, and are involved in screening people fleeing from the fighting. US President Donald Trump announced in December that with ISIS "defeated", he was ordering the withdrawal of some 2,000 US soldiers stationed in Syria. But with members of his own administration warning against a hasty withdrawal, the US military will likely stay in Syria until the end of April, <em>The Wall Street Journal</em> reported on Friday. Experts have warned that the end of the territorial “caliphate” will not mean the end of ISIS, which has already reverted to insurgent tactics in Iraq and Syria and retains affiliates in Africa, Central Asia and Southeast Asia. In January, four Americans were among 16 killed in a suicide bombing in the Syrian town of Manbij, which was later claimed by ISIS. In Iraq, ISIS is currently a more powerful terrorist organisation than Al Qaeda ever was, according to US intelligence assessments. “ISIS probably is still more capable than Al Qaeda in Iraq at its peak in 2006-2007, when the group had declared an Islamic State and operated under the name Islamic State of Iraq,” Pentagon spokesperson Sean Robertson told VOA last year. As the fighting in Syria reaches its final phases, the number of foreigners taken prisoner by the SDF has spiked. In recent days Canadian, German, Kazakh, and Azeri women have been among those fleeing. They join prisoners from at least 44 countries held in makeshift SDF prisons and detainment camps. With many foreign governments reluctant to repatriate citizens who supported ISIS, and Syria’s Kurds insisting they are unable to hold the prisoners long term, rights organisations have warned that foreign fighters face illegal rendition to Iraq. Human Rights Watch knows of at least five foreign detainees who were handed to Iraq’s Counter Terrorism Service by US forces after being captured in Syria, according to the group’s Iraq researcher Belkis Wille. "They are at risk of torture and unfair trials in Iraq," said Ms Wille. Iraqi courts have sentenced hundreds of foreigners for belonging to ISIS, often to death, and frequently after speedy trials lacking due process. International law prohibits the transfer of detainees to countries where they are at serious risk of torture and mistreatment.