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

The Ukrainian government said it was investigating reports of the use of chemical weapons in the city of Mariupol. The U.S. and U.K. are also working to verify the claims, with the U.K. government saying "all options are on the table" if they determine a chemical agent was used. Russian President Vladimir Putin made a rare appearance to defend what he called Ukraine's "noble" war and said peace talks had reached a dead end.