Russian troops have lost at least five service people for every Ukrainian soldier killed defending Donetsk Oblast’s Bakhmut, CNN reported, citing an unnamed NATO military official.

The official told CNN that the 5:1 ratio was an estimation based on the alliance’s intelligence, adding that Ukraine has also suffered significant losses on the Bakhmut front line.

The battle for Bakhmut, a city in Donbas region, has been raging for the past seven months. The Russian military is attempting to increase its grip over the entirety of Donetsk Oblast, around half of which it currently occupies.

The commander of the Ground Forces of Ukraine, Colonel General Oleksandr Syrskyi, said that the tensions surrounding Bakhmut had peaked as Russia threw even more Wagner mercenary forces onto the battlefield.