President Vladimir Putin said Russia had a "sufficient stockpile" of cluster bombs and reserved the right to use them if such munitions, the use of which he said he regarded as a crime, were deployed against Russian forces in Ukraine.
Ukraine said on Thursday it had received cluster bombs from the United States, its biggest military backer, which says the munitions are needed to compensate for shell shortages faced by Kyiv's forces at a time when they are mounting a counteroffensive.
Cluster munitions are banned in more than 100 countries because they typically release large numbers of smaller bomblets that can kill indiscriminately over a wide area. Some of them inevitably fail to explode and can pose a danger for decades, particularly to children.
Kyiv has said it will use cluster bombs to dislodge concentrations of enemy soldiers when trying to take back its own territory, but will not use them on Russian territory.
Putin told state TV Moscow would respond in kind if necessary.
"I want to note that in the Russian Federation there is a sufficient stockpile of different kinds of cluster bombs. We have not used them yet. But of course if they are used against us, we reserve the right to take reciprocal action."
