Ukraine conflict: What is a vacuum or thermobaric bomb?

Russia has been accused of planning to use thermobaric weapons - also known as vacuum bombs - in its invasion of Ukraine.

These are controversial because they are much more devastating than conventional explosives of similar size, and have a terrible impact on anyone caught in their blast radius.

A vacuum bomb, also called an aerosol bomb or fuel air explosive, consists of a fuel container with two separate explosive charges.

This can be launched as a rocket or dropped as a bomb from aircraft. When it hits its target, the first explosive charge opens the container and widely scatters fuel mixture as a cloud.

This cloud can penetrate any building openings or defences that are not totally sealed. A second charge then detonates the cloud, resulting in a huge fireball, a massive blast wave and a vacuum which sucks up all surrounding oxygen. The weapon can destroy reinforced buildings, equipment and kill or injure people.

They are used for a variety of purposes and come in a range of sizes - including weapons for use by individual soldiers such as grenades and hand-held rocket launchers.