Bring down and delete bridge interface that's up

Figured it out:

# ip link set br100 down
# brctl delbr br100

$ sudo ip link delete br0 type bridge

that's all

To clarify this for future.

ifup and ifdown are commands from some flavours of linux. And are used to control network settings set in /etc/network/interfaces for debian based systems and /etc/sysconfig/network-scripts/ifcg* on Redhat based systems (I cannot comment on others).

Creating and removing interfaces manually is done by using ifconfig (or ip which is bit more tricky to use). Bridges can be controlled with brctl

So after removing all interfaces from a bridge with brctl delif <bridg> <if> it can be moved to "down state" with ifconfig br100 down (or ip link set br100 down) and can now be removed with brctl delbr br100

Please note that using network-manager to manage your networks might make your manually changed interfaces to reset.