'You ain't no Muslim, bruv'. I will stand by THAT Muslim anytime,' wrote one social media user.
Another supporter said:'#YouaintnoMuslin, London cannot be broken. Sums up our unity perfectly.'
The knifeman slashed a man at a busy London tube station and allegedly shouted 'this is for Syria' before being Tasered by police in what has been described by Scotland Yard as a terrorism attack.
The victim suffered serious knife injuries at Leytonstone underground station shortly after 7pm.
Eyewitnesses claimed they could hear 'this is for Syria' and 'all of your blood will be spilled' during the terrifying attack.
One bystander called out: 'Drop it, you fool' as the man was held down by police. There were also claims that bottles were hurled at the arrested man as he was led away by police.
After reportedly slashing his victim's throat, the man allegedly threatened several other passengers before being confronted by a number of unarmed police officers.
The officers ordered the man to drop his weapon, who continued to wave the large knife.
One video shows the man lunge towards the police, with witnesses shouting 'he's stabbed someone'.
One of the officers reportedly shouted 'Tazer, Tazer, Tazer' before discharging the weapon.