The violence that erupted during the traditional Unionist marching season in Northern Ireland, injuring 21 police officers, was organised, according to the police. Missiles including homemade explosive devices, fireworks and stones were thrown at officers as unrest flared in various cities and town throughout the province. In the capital, Belfast, shots were fired at police officers.

Police said the trouble was orchestrated to shake the peace process in Northern Ireland which is in place since 1998. Tensions are normally heightened between the pro-Irish Republican and the pro-British Unionist communities during the marches, held by Protestant Orangemen each year.

Several of the parades have become flashpoints over the years because they go directly and provocatively through Catholic neighbourhoods. The marches mark the victory of Protestant King William of Orange over James II's Catholics in Ireland in 1690.

Devolved self-rule is now in place in Northern Ireland after a landmark agreement in 2002 between the Loyalist Democratic Unionists (DUP) and the Republican Sinn Fein.

photo by trawets1 (flickr)