Police have arrested five young men across the UK capital on suspicion of travelling to join a banned terror group.
It follows raids at four separate properties in January. The group range in age from 15 to 19. All five are being questioned at a central London police station.
Scotland Yard did not give any further information at this stage on which organisation the teenagers were trying to join.
"Officers from the MPS Counter Terrorism Command have today, Monday 20 February, arrested five males under 20-years-old on suspicion of Preparation of Terrorist Acts, Contrary to Section 5 of the Terrorism Act 2006," a Met Police spokesman said.
"The arrests follow searches at four residential addresses in London on Tuesday, 14 January. This morning a 17-year-old male and a 16-year-old male were arrested at separate residential addresses in south London; two other teenagers - 17-year-old male and a 19-year-old male - were arrested at a residential address in west London.
"A further residential address was searched in Lambeth earlier today in connection with the investigation. Officers have since made a further arrest. A 15-year-old boy was arrested this evening in east London and officers are presently searching the residential address where he was arrested.
"All five have been detained under TACT and are at present in a central London police station pending further enquiries. The arrests relate to plans to travel to join a proscribed organisation."
According to a UK government report, there were 255 terrorism-related arrests in Britain for the year ending 31 March 2016. The only age group to see a rise in the number of arrests was under-18-year-olds, which saw a small increase from eight arrests in the year ending 31 March 2015, to 14 in the year ending 31 March 2016.
Max Hill QC was named on 20 February as the new independent reviewer of terrorism legislation. He replaces human rights lawyer David Anderson QC, who warned that the government's anti-radicalisation strategy, Prevent, is not trusted by "a very large number of decent British Muslims".