Russian President Vladimir Putin said his country had enough cluster munitions to answer if Ukraine was to use the weapons, in an interview published on Sunday.

Ukraine started receiving cluster weapons from the United States, a move that sparked concerns due to the long-term risk posed to civilians by bomblets that fail to explode.

“Russia has a sufficient stockpile of various kinds of cluster munitions,” Putin told a state-television journalist.

The controversial weapons can disperse up to several hundred small explosive charges, which can remain unexploded in the ground.

“If they are used against us, we reserve ourselves the right to tit-for-tat actions,” Putin said.

He added Russia had not yet used the weapons despite a “certain shortage of munitions at some point”.

Human Rights Watch and Ukrainian forces have accused Russia of already using cluster munitions on the battlefield.

They are banned by numerous countries — notably in Europe — that are signatories to a 2008 Oslo Convention, to which neither Russia, the United States nor Ukraine are parties.

Humanitarian groups have strongly condemned the US decision to supply cluster munitions to Ukraine.

US President Joe Biden said the decision was “very difficult” but stressed Ukraine needed extra ammunition to refill its depleted stocks.