Hundreds of Hong Kong national security police raided the office of online pro-democracy media outlet Stand News on Wednesday and arrested six people, including senior staff, for “conspiracy to publish seditious publications.”

The raid further raises concerns about freedom of speech and that of the media in the former British colony, which returned to Chinese rule in 1997 with the promise that a wide range of individual rights would be protected.

Police said in a statement that they had a warrant authorizing officers “to search and seize relevant journalistic materials.”

“Over 200 uniformed and plainclothes police officers have been deployed during the