Activists have described the largest protest against the 1968 Soviet-led Warsaw Pact invasion in nearly two decades as "an important political moment" evidencing a new attitude in Czechoslovakia.

Thousands of people marched through the capital Sunday night in the biggest protest since 1969 against the Aug. 20-21, 1968 invasion that crushed the experiment in democracy known as the "Prague Spring."The official news agency CTK said 28 people were still in detention Monday after police arrested 77 people in Prague in what it termed "disturbing actions" that "grew into hooliganism."

Six of the seven unidentified foreigners detained were expelled, CTK said without further details.