Two men have been arrested on suspicion of the commission, preparation or instigation of acts of terrorism, police have said.
The men, aged 18 and 32, are being held at a central London police station under the Terrorism Act 2000, Scotland Yard said.
Two addresses in east London are being searched by police.
The investigation is still in its early stages, but the arrests are not thought to be linked to any significant plot.
The Press Association, photo by Ventlindown