LONDON - Britain's terror threat level will remain at "severe" after militants killed seven people and injured 48 in London, Prime Minister Theresa May said on Monday, describing the assault as an attack on the free world. Additional security measures have been put in place, including at several bridges in central London, May said. Three knife-wielding assailants rammed a van into pedestrians on London Bridge and stabbed others nearby."JTAC, the independent joint terrorism analysis center, have confirmed that the national threat level remains at severe, that means that a terrorist attack is highly likely," she told BBC television after a meeting of the government's emergency committee."It is now clear that, sadly, victims came from a number of nationalities. This was an attack on London and the United Kingdom, but it was also an attack on the free world."