Russian President Vladimir Putin says Russia is thinking about possible changes to its doctrine on the use of nuclear weapons.
The existing doctrine states that Russia may use such weapons in response to a nuclear attack or in the event of a conventional attack that poses an existential threat to the state.
Since the start of the war in Ukraine, some hawks among Russian military analysts have been advocating that Russia should lower its threshold for nuclear use.
Putin said, however, that there was no need for Russia to carry out a pre-emptive nuclear strike.
He was speaking to reporters a day after visiting nuclear-armed North Korea for a summit with its leader, Kim Jong-un.
The two leaders signed a treaty under which each side promised to provide immediate military assistance to the other in the event of armed aggression against either one of them.
State media quoted Putin as saying that Russia expected that its co-operation with North Korea would serve as a deterrent to the US and its allies but that there was no need to use North Korean soldiers in the war in Ukraine.
Putin also said he did not rule out Russia supplying high-precision weapons to North Korea.
Russian forces attacked a village in Ukraine's eastern Donetsk region on Thursday, killing three people and injuring four more, including a child, prosecutors said.
The village of Rozkishne, about 25km from the front line, was targeted by the strike, regional prosecutors said on Telegram.
According to preliminary data, Russian troops used the Smerch system to launch cluster munitions, prosecutors said.
Among the injured was a 14-year-old boy who was hospitalised.
Four households, cars and a gas pipeline were damaged in the attack, prosecutors added.
