London metro station incident caused by bomb, top UK police officer says

LONDON (Reuters) - British police said a bomb was used during an explosion at a London metro station which injured 18 people in what officers described as a "terrorist incident." "We now assess that this was a detonation of an improvised explosive device," Britain's top counter-terrorism officer Mark Rowley said on Friday. London's police is being supported by Britain's MI5 intelligence service, he said. (Reporting by Kate Holton and Michael Holden; writing by Costas Pitas; editing by Guy Faulconbridge)