Russia-Ukraine conflict: What would Nato do if Russia used chemical weapons?

The Ukrainian government says it is investigating reports about the use of chemical weapons in the city of Mariupol.

The US and the UK are also working to verify the claims, and the UK government says ‘all options are on the table’ should they determine that chemical agents were used.

Russian President Vladimir Putin has made a rare appearance, defending what he called his ‘noble’ war in Ukraine – and saying that peace talks have reached a dead end.