Russian officials say President Vladimir Putin will convene a security council meeting on Monday following the explosion on a key bridge linking Crimea and Russia.

The presidential office has not made public what the council will discuss.

But Putin may take up Saturday's blast. He blamed Ukraine for the incident, calling it a terrorist act.

On Sunday, presidential spokesperson Dmitry Peskov did not give a clear answer when Russia's state-run news agency asked if the basic principles on the use of nuclear weapons will be applied following the explosion.

The Putin administration has been threatening to use such weapons.

Last month, former President Dmitry Medvedev wrote on social media that conditions for Russia's use of nuclear arms include a nuclear attack against the country and an act of aggression using conventional weapons that threatens the very existence of the state.

Medvedev now serves as the deputy chairman of the security council.