Ukrainian troops have started using a weapon that has been criticized by humanitarian groups. They have begun deploying cluster bombs on the battlefield.

Many countries ban the weapons because they pose a danger to civilians. However, the US sent them to Ukraine due to a shortage of other types of munitions.

White House National Security Council spokesperson John Kirby said on Thursday that they are already having an impact.

Kirby said, "I would just tell you that they're using them appropriately. They're using them effectively."

Russia is another country that allows the use of cluster bombs. President Vladimir Putin said on Sunday that his military has them in "sufficient" numbers. He warned that his troops would "retaliate" if Ukrainians used the weapons against them.