Russia’s military has advanced to within 12 miles of the northeastern Ukrainian city of Sumy, intensifying operations around the regional capital, the Wall Street Journal reported Sunday.

After Ukrainian units withdrew from Russia’s Kursk region in late April, the Russian army entered Ukrainian territory and has since assembled 50,000 troops in the region, WSJ said.

According to Ukrainian soldiers who spoke to WSJ, Russian forces outnumber Ukrainian units three to one.

This month, Ukraine deployed the “Timur” Special Forces Unit to positions near Sumy, attempting to slow Russian advances.

Kappa, a commander in the unit, said in an interview with WSJ that Russian “numbers are a big problem for us, though not enough to overrun us.”

“The enemy is losing 300 to 400 people per day across the region. But they can deal with that level of casualties…They keep bringing in reserves.”

Large-scale assaults, described within the Russian military as “meat assaults,” have become a primary tactic, independent military analyst Yan Matveev told The Washington Post.