HONG KONG — A representative of Reporters Without Borders was deported from Hong Kong upon arrival Wednesday, the advocacy group said, in what it called a “new decline” in press freedom in the Chinese territory.

Aleksandra Bielakowska, an advocacy officer for Reporters Without Borders who is based in Taiwan, was detained for six hours at Hong Kong International Airport, the Paris-based group said in a statement. She was questioned and her belongings were searched three times before she…