Demosisto said Chow was arrested at her home and taken to Wan Chai Police Station.
The group said police had arrested Wong at about 7.30am, bundling him into a private car while on his way to South Horizons MTR Station.
Police said Wong was arrested on suspicion of organising, taking part and inciting others to join an unauthorised assembly on June 21, when protesters surrounded police headquarters in Wan Chai.
Chow is suspected of taking part and inciting others to join an unauthorised assembly, police said.
The arrests of the two 22-year-olds came just hours after the former leader of the now banned Hong Kong National Party, Chan Ho-tin, said he was detained at the airport while preparing to board a flight.
The police on Friday morning issued a statement confirming that a 29-year-old man surnamed Chan was arrested on Thursday night at the airport on suspicion of taking part in a riot and assaulting police.
Demosisto’s vice-chairman Isaac Cheng said the government is trying to scare people into staying away from protests.
“The government is spreading white terror in the whole atmosphere of Hong Kong and it is frightening Hong Kong people not to come out again to fight for the rights they deserve,” Cheng said.
“So we urge Hong Kong people to come out in every circumstance, for every assembly and protest, to make Hong Kong become Hong Kong again.”
Last updated: 2019-08-30 HKT 11:31