Hong Kong's chief executive says "external forces" are involved in pro-democracy protests that have occupied parts of this financial capital for more than three weeks.

Chief Executive Leung Chun-ying said in a televised interview Sunday that "there is obviously participation by people, organizations from outside of Hong Kong." Leung said they came from "different countries in different parts of the world," but didn't specify which countries.

The comments mark the first time Leung has alleged outside involvement in the protests. China's central government has for weeks accused outside groups of stirring up the unrest but has not produced evidence backing up the claims.

The Hong Kong Federation of Students immediately rejected the accusations, with Secretary General Alex Chow saying Leung was "just making it up."