Kristi Noem said she "hated" the dog as it behaved like a "trained assassin," and was "dangerous to anyone she came in contact with"
The incident near the Westfield shopping centre in Stratford was not being treated as terror-related, a police spokesman said.
"A number of people have been reported injured at different locations - believed to be six people. We await further details," London's Metropolitan Police said in a statement.
One male was arrested on suspicion of causing grievous bodily harm, the statement said.