British intelligence agencies intercepted the communications of foreign politicians in London for the 2009 G20 summit, the Guardian reports.
The details were revealed in documents uncovered by NSA whistleblower Edward Snowden.
The Guardian reports the documents reveal that during meetings in April and September 2009, the GCHQ (Government Communications Headquarters) used "ground-breaking intelligence capabilities" to intercept the communications of delegates.
Methods included tricking delegates into using fake internet cafes so spy agencies could read their emails and hacking the delegates' BlackBerrys to allow emails and phone calls to be monitored.
British allies Turkey and South Africa were among those targeted.
