One of the protesters, Chris Howson, told the Newham Recorder that arms fairs like this one were "fuelling the wars of tomorrow".
He said: "We are here to pray for peace because most people have no idea that they are selling weapons that can be used to kill women and children.”
More top news
Scotland Yard confirm that two people arrested in connection with the attack on Westminster have been released with no further action
An appeal to support the family of murdered policeman Keith Palmer has reached more than £700,000 in two days.
PC Keith Palmer will be remembered permanently at the National Memorial Arboretum, Home Secretary Amber Rudd has said.