Among those arrested were 81-year-old activist and former lawmaker Martin Lee and democracy advocates Albert Ho, Lee Cheuk-yan and Au Nok-hin.
Police also arrested media tycoon Jimmy Lai, who founded the local newspaper Apple Daily.
Lai, Lee Cheuk-yan and Yeung Sum — a former lawmaker from the Democratic Party — were charged in February over their involvement in a mass anti-government demonstration on Aug. 31 last year. The protests in the semi-autonomous Chinese territory against proposed extradition legislation exposed deep divisions between democracy-minded Hong Kongers and the Communist Party-ruled central government in Beijing.
The bill — which would have allowed Hong Kong residents to be sent to mainland China to stand trial — has been withdrawn, but the protests continued for more than seven months, centered around demands for voting rights and an independent inquiry into police conduct.
While the protests began peacefully, they increasingly descended into violence after demonstrators became frustrated with the government’s response. They feel that Hong Kong leader Carrie Lam has ignored their demands and used the police to suppress them.
The League of Social Democrats wrote in a Facebook post on Saturday that its leaders were among those arrested, including chairman Raphael Wong. They were accused of participating in two unauthorized protests on Aug. 18 and Oct. 1 last year.