The Russian military has issued a warning over the growing presence of ISIS in Afghanistan as they announced they would increase the combat capabilities of its military base in Tajikistan.

This warning comes days after the Russian Foreign Ministry claimed that US forces are cooperating with the terrorist group by transferring its fighters across the region. According to Foreign Ministry Spokeswoman Maria Zakharova, Russia is aware of unmarked helicopters conducting flights in areas where ISIS remains active.

“It would have been impossible to carry out such activities unbeknownst to the US and NATO forces that had complete control of Afghanistan’s airspace,” Zakharova told TASS news agency.

The news follows recent revelations by commanders of Iraq’s Popular Mobilization Units claiming that thermal cameras captured US helicopters transporting ISIS fighters in Iraq.