The rioters were forcibly removed from the square.
Literal
Rioters [topic-は] plaza [from-から] forcibly were-removed.
排除された is the passive of 排除する (to remove/eliminate). 強制的に (forcibly) uses the ~的に pattern that turns a sino-Japanese noun into an adverb — 強制 (coercion) → 強制的に (forcibly). から marks the source. A formal, news-register sentence.