English Defence League supporters have thrown missiles at police in Woolwich after a machete attack that left one man dead.
A group of between 75 and 100 men gathered at The Queen's Arms pub on Burrage Grove, where they sang nationalistic songs.
Sky News correspondent Alistair Bunkall, who is at the scene, said: "As soon as the EDL got into the town centre ... it became not only a lot harder for the police to try and contain anything, but also the aggression (increased) quite considerably.
"A few missiles have been thrown, glass bottles and the like. The police are trying to surround them and they've been charging them as well with batons."
It came after two men were arrested following separate attacks on mosques hours after the suspected terrorist incident in Woolwich.
A 43-year-old man is in custody on suspicion of attempted arson after reportedly walking into a mosque with a knife in Braintree, Essex.
Local MP Brooks Newmark said on this Twitter account: "Local mosque in Braintree attacked by man with knives and incendiary device. Man arrested. No one injured.
"Just met with leaders of local mosque in Braintree which was attacked this evening. Thanked local police for their swift response."
Essex Police confirmed a 43-year-old from Braintree had been arrested on suspicion of possession of an offensive weapon and attempted arson after the incident in Silks Way at 7.15pm.
Meanwhile police in Kent were called to reports of criminal damage at a mosque in Canterbury Street, Gillingham, at 8.40pm.
A spokesman said a man was in custody on suspicion of racially-aggravated criminal damage.