Iraq's elite counterterrorism forces say they have entered the center of a strategically important western Islamic State-held town.

Government forces reached the center of Hit on Wednesday. The operation to retake the small Euphrates river town — initially launched last month — was stalled by politics, heavy IS resistance and tens of thousands of trapped civilians.

Iraqi troops first entered Hit on Monday under cover of heavy airstrikes. Since the operation was relaunched last week the U.S. led coalition launched more than 18 strikes on the town.

Hit sits along an IS supply line that links territory controlled by the extremist group in Iraq and in Syria. Through the line, IS ferries fighters and supplies from Syria into Iraq.