Far-right organisation English Defence League has called on its supporters to gather in Woolwich to protest in response to today's attack.
Leading members have called for people to "take to the streets" and asked them to join a local division of the organisation.
One message, posted online, asked members to get to London "...now if possible."
More top news
A list of commemorative events as the UK marks a decade to the day 52 were killed and hundreds injured in London terror attacks.
Larger stores could be allowed to open beyond the current six-hour limit on Sundays under a relaxation of rules in Wednesday's Budget.
IS is now attracting women and whole families as well as young men - but will any return to carry out another 7/7?