Around 100 protesters, believed to be English Defence League supporters, are holding unplanned protests in two areas of Manchester.
There are also reports of a counter-protest by members of Unite Against Fascism in another part of the city.
Greater Manchester police have told ITV Granada that one person has been arrested on suspicion of a public order offence.
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The foreign secretary has criticised internet and social media giants for failing to detect and remove extremist material posted online.
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