believe it was an assassination attempt on president putin. let s take you straight to these videos claiming to show the attack. this is the moment of the explosion coming up the moment of the explosion coming up now. there it is. that is circulating on social media. it appears to be a drone flying in from the left hand side before that explosion. we can t be sure of course. this is unverified footage at the moment. here is the drum from another angle, again not verified. shortly you will see the smoke coming up. according to our teams the videos do appear to be taken at the videos do appear to be taken at the time and location claimed. ukraine has denied carrying out any attack and claims russia is using this accusation as a cover to launch an attack. earlier i spoke to wil vernon in our moscow bureau and i were russia editor at bbc monitoring. started by asking will what exactly the russian authorities have said. the what exactly the russian authorities have said. , ., ., h