Baghdad - Iraqi troops in Mosul have battled their way to the Tigris River running through the centre of town, marking a milestone in the nearly three-month-old offensive aimed at reclaiming the northern city from Islamic State militants.Lt Gen Abdul-Amir Rasheed Yar Allah said special forces reached the river late on Sunday and now control the eastern side of one of the city's five bridges, all of which have been disabled by US-led airstrikes in support of the offensive.Prime Minister Haider al-Abadi said the recent advances were "big achievements for all the factions of the Iraqi security forces.""Thank God, our forces are liberating neighbourhood after neighbourhood," he said on Monday in a joint press conference with his Jordanian counterpart in Baghdad.In Mosul, Major General Sami al-Aridi of the special forces told The Associated Press that troops were battling ISIS in the Baladiyat and Sukar neighbourhoods after driving the extremists out of Muthana and Rifaq the day before. He said Iraqi forces repelled an overnight attack, killing 37 militants, without elaborating.The Mosul offensive resumed last month after a two-week lull due to stiff ISIS resistance and bad weather. Since then, Iraqi forces have recaptured new areas in the city's eastern half after receiving reinforcements.Mosul is Iraq's second largest city and the extremist group's last major urban bastion in the country. Iraqi special forces have done most of the fighting within the city, while Iraqi troops have advanced on it from different sides. Kurdish forces and Shiite militias have driven ISIS from surrounding areas and sought to cut off militant escape routes.Mosul fell to ISIS in the summer of 2014, when the extremists swept across much of northern and western Iraq. Iraqi forces have gradually retaken most of that territory over the past three years, and outside of Mosul the militants are largely confined to smaller towns and villages.