The storming of British Embassy compounds by Iranian protesters complicates the search for a negotiated solution to the standoff over Tehran's nuclear programme, and appears to reflect infighting among Iranian factions.

UK's prime minister David Cameron has warned Iran of serious consequences following what Britain has labelled an outrageous and irresponsible attack.

Britain has been at the forefront of the international campaign for tougher sanctions against Iran over its nuclear programme, which Britain and other Western countries suspect is aimed at developing a nuclear weapon but Tehran insists is peaceful.

Al Jazeera's Dorsa Jabari reports from Tehran.