On 21 July 2005, four attempted bomb attacks by four Islamist extremists disrupted part of London's public transport system as a follow-up attack to the 7 July 2005 London bombings two weeks earlier. The explosions occurred around midday at Shepherd's Bush, Warren Street and Oval stations on the London Underground, and on London Buses route 26 in Haggerston. A fifth bomber dumped his device without attempting to set it off.
Connecting lines and stations were closed and evacuated. Metropolitan Police later said the intention of the attack was to cause large-scale loss of life, but only the detonators of the bombs exploded, probably causing the popping sounds reported by witnesses; a person having a minor asthma attack was the only reported injury.