Chanting "LSE should be free" and "free education now", some 300 students held an unauthorised protest organised by a student group calling itself Occupy LSE which has barricaded itself in one of the buildings.
The movement is demanding "an education that is liberating -- which does not have a price tag" and calling for tuition fees to be scrapped.
Student fees are a highly sensitive political issue in Britain, which holds a general election on May 7.
Fees for university students in England were introduced in 1998.
The LSE -- whose alumni include Mick Jagger, John F. Kennedy and Karl Popper -- specialises in political science and economics and has a long history of student demonstrations, particularly in the 1960s.
