HONG KONG — Reporters Without Borders, which advocates press freedom, announced on Thursday that it would open its first Asian bureau in Taipei, Taiwan’s capital, rather than in Hong Kong, which is increasingly under China’s sway.

“Hong Kong was the place where we originally wanted to open an office in Asia,” Christophe Deloire, the group’s secretary general, said in an email, adding, “It is not so easy now to run activities from there.”

Mr. Deloire said that the Paris-based organization, also known as Reporters Sans Frontières, decided against Hong Kong because of “a lack of legal certainty for our entity and activities.” He also cited the possibility that staff members would be put under surveillance.

The announcement is a reversal of fortune for both Hong Kong and Taiwan. When Reporters Without Borders was founded in 1985, Hong Kong was a British colony with a high degree of press freedom, while Taiwan was at the tail end of four decades of martial law.