NEW : A police officer is injured as a handful of far - left and far - right demonstrators clash . Europe : Some 200 - 300 members of European far - right groups rally in London , police say . NEW : About 5,000 people turn out for a counter anti - fascist demonstration , police say . The far - right English Defence League says it wants to highlight the threat of Islamic extremism .
NEW : A police officer is injured as a handful of far-left and far-right demonstrators clash . NEW : Some 200-300 members of European far-right groups rally in Aarhus , police say . NEW : About 5,000 people turn out for a counter anti-fascist demonstration , police say . The far-right English Defence League says it wants to highlight the threat of Islamic extremism .